POST-EFFECTIVE
                                 AMENDMENT NO. 1
                                   ON FORM S-3
                                       TO
                                   FORM S-1/A
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                            CECO ENVIRONMENTAL CORP.
             (Exact Name of Registrant as Specified in its Charter)
                                    DELAWARE
         (State or Other Jurisdiction of Incorporation or Organization)

                                   13-2566064
                      (I.R.S. Employer Identification No.)

                               3120 Forrer Street
                             Cincinnati, Ohio 45209
                                 (513) 458-2600

                    Registrant's Principal Executive Offices
    (Address, Including Zip Code, and Telephone Number, Including Area Code)

                              Phillip DeZwirek, CEO
                            CECO Environmental Corp.
                               3120 Forrer Street
                             Cincinnati, Ohio 45209
                                 (513) 458-2600

 (Name, Address, Including Zip Code, and Telephone Number, Including Area Code,
                              of Agent for Service)

                                    Copy to:
                                 Leslie J. Weiss
                          Sugar, Friedberg & Felsenthal
                       30 North LaSalle Street, Suite 3000
                             Chicago, Illinois 60602
                                 (312) 704-9400

Approximate Date of Commencement of Proposed Sale to the Public: From time to
time after the effective date of this Registration Statement as determined by
the Selling Stockholders.

If the only securities being registered on this Form are being offered pursuant
to dividend or interest reinvestment plans, please check the following box. [ ]

If any of the securities being registered on this Form are to be offered on a
delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, as amended (the "Securities Act") other than securities offered only in
connection with dividend or interest reinvestment plans, check the following
box. [X]

If this Form is filed to register additional securities for an offering pursuant
to Rule 462(b) under the Securities Act, please check the following box and list
the Securities Act registration statement number of the earlier effective
registration statement for the same offering. [ ]

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under
the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [X] 333-85146

If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]




THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE
A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT
SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF THE
SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A),
MAY DETERMINE.

This Prospectus is not an offer to sell these securities and is not soliciting
an offer to buy these securities in any state where the offer or sale is not
permitted.

                   SUBJECT TO COMPLETION, DATED APRIL 30, 2003

                                  Common Stock
                                2,074,002 Shares

                            CECO ENVIRONMENTAL CORP.

        This Prospectus relates to the sale of up to 2,074,002 shares of our
common stock that may be offered for sale or otherwise transferred from time to
time by one or more of the selling shareholders identified in this Prospectus.
We are registering 1,706,668 shares of common stock and 367,334 shares of common
stock issuable upon exercise of warrants of CECO Environmental Corp. ("CECO" or
the "Company"). The prices at which the stockholders may sell the shares will be
determined by the prevailing market price for the shares or in negotiated
transactions. We will not receive any of the proceeds from the sale of shares by
the selling stockholders. Our common stock is traded on the Nasdaq SmallCap
Market under the symbol "CECE". The closing sale price of the common stock on
March 27, 2003 on the Nasdaq was $1.84 per share.

        Information contained in this prospectus is not complete and may be
changed. The selling shareholders cannot sell their common stock until the
registration statement filed with the Securities and Exchange Commission becomes
effective. This prospectus is not an offer to sell the securities and it is not
soliciting an offer to buy the securities in any State where the offer or sale
is not permitted.

                                   ----------

        THIS INVESTMENT INVOLVES A HIGH DEGREE OF RISK. THE SHARES SHOULD ONLY
BE PURCHASED BY PERSONS WHO CAN AFFORD A COMPLETE LOSS. SEE "RISK FACTORS,"
BEGINNING ON PAGE 2.

        NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS
PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

                 The date of this Prospectus is April 30, 2003.




                                    OVERVIEW

        CECO was incorporated in New York State in 1966 and reincorporated in
Delaware in January 2002. We operate as a provider of air pollution control
products and services. We market our products and services under the following
trade names: "Kirk & Blum", "kbd/Technic", "CECO Filters", "Busch
International", "CECO Abatement Systems", and "K&B Duct".

The Offering

        We issued 1,000,000 of the shares of common stock described in this
Prospectus to certain of the selling stockholders upon the exercise of warrants.
These warrants had been acquired from us on December 7, 1999 in a private
transaction and are considered "restricted securities" under the Securities Act
of 1933 (the "Securities Act"). In December 2001, we received gross proceeds of
$2,250,000 from the exercise of these warrants.

        On December 31, 2001, we completed the sale of 706,668 shares of our
common stock, at a price of $3.00 per share, and the issuance of warrants
("Investor Warrants") to purchase 353,334 shares of our common stock at an
initial exercise price of $3.60 per share, to a group of accredited investors
led by Crestview Capital Fund L.P., a Chicago-based private investment fund (the
"Investors"). As a finder's fee pursuant to an agreement with The Shemano Group,
we also issued warrants to purchase 14,000 shares of our common stock at an
initial exercise price of $3.60 (such warrants collectively with the Investor
Warrants, the "Warrants") to five of the selling shareholders. All of the shares
underlying the Warrants are included in this Prospectus. More information on the
selling stockholders is provided in the section entitled "Selling Stockholders."

        The offering price of the shares will be determined at the time of sale
by the selling shareholders. As of March 31, 2003, there were 9,589,736 shares
outstanding, including the 706,668 shares sold pursuant to the private
financing, but excluding the 367,334 shares that may be purchased by exercise of
the Warrants. We will not receive any of the proceeds from the shares offered by
the selling shareholders. We intend to use the proceeds from the exercise of the
Warrants, if exercised, held by certain selling shareholders for working capital
purposes.

        The selling stockholders may sell the shares in public or private
transactions, on or off the Nasdaq market, at prevailing market prices, or at
privately negotiated prices. The selling stockholders may sell shares directly
to purchasers or through brokers or dealers. Brokers or dealers may receive
compensation in the form of discounts, concessions or commissions from the
selling stockholders. The selling stockholders may be deemed to be
"underwriters" within the meaning of the Securities Act. Any commissions
received by a broker or dealer in connection with resales of the shares may be
deemed to be underwriting commissions or discounts under the Securities Act.
More information is provided in the section entitled "Plan of Distribution."

        This Prospectus registers the shares of common stock under the
Securities Act and allows for future sales by the selling stockholders to the
public without restriction. We have agreed to pay for the preparation and filing
of the registration statement and this Prospectus.

                                        1



        The principal office of CECO is 3120 Forrer Street, Cincinnati, Ohio
45209, telephone number (513) 458-2600.

                                  RISK FACTORS

        An investment in the shares being offered hereby involves a high degree
of risk. In deciding whether to purchase shares of our common stock, you should
carefully consider the following risk factors. INVESTING IN THESE SHARES IS
SPECULATIVE AND INVOLVES A HIGH DEGREE OF RISK. THE SHARES SHOULD NOT BE
PURCHASED BY ANYONE WHO CANNOT AFFORD THE LOSS OF THEIR ENTIRE INVESTMENT.

        In addition to the other information on this Prospectus, the factors
listed below should be considered in evaluating our business and prospects. This
Prospectus contains a number of forward-looking statements that reflect our
current views with respect to future events and financial performance. These
forward-looking statements are subject to certain risks and uncertainties,
including those discussed below and elsewhere herein, that could cause actual
results to differ materially from historical results or those anticipated. In
this report, the words "anticipates," "believes," "expects," "intends," "future"
and similar expressions identify forward-looking statements. Readers are
cautioned to consider the specific factors described below and not to place
undue reliance on the forward-looking statements contained herein, which speak
only as of the date of this Prospectus. We assume no obligation to publicly
update any forward-looking statements.

Operating at a Loss

        We have incurred net losses for our past 3 fiscal years. There are no
assurances that we will achieve or sustain profitability.

Competition

        The industries in which we compete are all highly competitive. We
compete against a number of local, regional and national contractors and
manufacturers in each of our business segments, many of which have been in
existence longer than us and some of which have substantially greater financial
resources than we do. We believe that any competition from new entrants that are
large corporations may be able to compete with the Company on the basis of price
and as a result may have a material adverse affect on the results of our
operations. In addition, there can be no assurance that other companies will not
develop new or enhanced products that are either more effective than ours or
would render our products non-competitive or obsolete.

Dependence On Key Personnel

        We are highly dependent on the experience of our management in the
continuing development of its operations. The loss of the services of certain of
these individuals, particularly Richard J. Blum, President of CECO, would have a
material adverse effect on our business. Our future success will depend in part
on our ability to attract and retain qualified personnel to manage our
development and future growth. There can be no assurance that it will be
successful in

                                        2



attracting and retaining such personnel. The failure to recruit additional key
personnel could have a material adverse effect on our business, financial
condition and results of operations.

Continued Control By Management

        As of the date of this Prospectus, management of CECO beneficially owns
approximately 54% of the Company's outstanding common stock, assuming the
exercise of currently exercisable warrants and options held by management.
CECO's stockholders do not have the right to cumulative voting in the election
of directors. Accordingly, present stockholders will be in a position to exert
control over our business and operations, including the election of directors of
CECO.

Dependence Upon Third-Party Suppliers

        Although we are not dependent on any one supplier, we are dependent on
the ability of our third-party suppliers to supply our raw materials, as well as
certain specific component parts. We purchase all of our chemical grade
fiberglass from one domestic supplier, which we believe is the only domestic
supplier of such fiberglass, and certain specialty items from only two domestic
suppliers. These items also can be purchased from foreign suppliers. Failure by
our third-party suppliers to meet our requirements could have a material adverse
effect on us. There can be no assurance that our third-party suppliers will
dedicate sufficient resources to meet our scheduled delivery requirements or
that our suppliers will have sufficient resources to satisfy our requirements
during any period of sustained demand. Failure of manufacturers or suppliers to
supply, or delays in supplying, our raw materials or certain components, or
allocations in the supply of certain high demand raw components could materially
adversely affect our operations and ability to meet our own delivery schedules
on a timely and competitive basis.

Patents

        We hold various patents and licenses relating to certain of our
products. There can be no assurance as to the breadth or degree of protection
that existing or future patents, if any, may afford us, that our patents will be
upheld, if challenged, or that competitors will not develop similar or superior
methods or products outside the protection of any patent issued to us. Although
we believe that our products do not and will not infringe patents or violate the
proprietary rights of others, it is possible that our existing patent rights may
not be valid or that infringement of existing or future patents or proprietary
rights may occur. In the event our products infringe patents or proprietary
rights of others, we may be required to modify the design of our products or
obtain a license for certain technology. There can be no assurance that we will
be able to do so in a timely manner, upon acceptable terms and conditions, or at
all. Failure to do any of the foregoing could have a material adverse effect
upon our business. In addition, there can be no assurance that we will have the
financial or other resources necessary to enforce or defend a patent
infringement or proprietary rights violations action which may be brought
against us. Moreover, if our products infringe patents or proprietary rights of
others, we could, under certain circumstances, become liable for damages, which
also could have a material adverse effect on our business.

                                        3



New Product Development

        The air pollution control and filtration industry is characterized by
ongoing technological developments and changing customer requirements. As a
result, our success and continued growth depend, in part, on our ability in a
timely manner to develop or acquire rights to, and successfully introduce into
the marketplace, enhancements of existing products or new products that
incorporate technological advances, meet customer requirements and respond to
products developed by our competition. There can be no assurance that we will be
successful in developing or acquiring such rights to products on a timely basis
or that such products will adequately address the changing needs of the
marketplace.

Technological And Regulatory Change

        The air pollution control and filtration industry is characterized by
changing technology, competitively imposed process standards and regulatory
requirements, each of which influences the demand for our products and services.
Changes in legislative, regulatory or industrial requirements may render certain
of our filtration products and processes obsolete. Acceptance of new products
may also be affected by the adoption of new government regulations requiring
stricter standards. Our ability to anticipate changes in technology and
regulatory standards and to develop and introduce new and enhanced products
successfully on a timely basis will be a significant factor in our ability to
grow and to remain competitive. There can be no assurance that we will be able
to achieve the technological advances that may be necessary for us to remain
competitive or that certain of our products will not become obsolete.

Leverage

        We are highly leveraged. CECO currently has loan facilities, including a
term loan and line of credit, with PNC Bank, National Association; Bank One,
N.A.; and Fifth Third Bank. The terms of such loan facilities have been revised
through seven separate amendments in order to alter some of the financial
covenants made by us to prevent CECO from being in default of such covenants.

Our Common Stock Has Been Relatively Thinly Traded And We Cannot Predict The
Extent To Which A Trading Market Will Develop

        Our common stock trades on the Nasdaq SmallCap Market. Our common stock
is thinly traded compared to larger, more widely known companies. Thinly traded
common stock can be more volatile than common stock trading in an active public
market.

Our Financial Performance Is Sensitive To Changes In Overall Economic Conditions

        A general slowdown in the United States economy may adversely affect the
spending of our customers, which would likely result in lower net sales than
expected on a quarterly or annual basis. Future economic conditions, such as
business conditions, fuel and energy costs, interest rates, and tax rates, could
also adversely affect our business by reducing customer spending.

                                        4



We May Need To Obtain Additional Financing

     Management believes that with cash on hand and proceeds from expected sales
that it has sufficient proceeds to meet cash requirements for the next twelve
months.

        However, we may need to raise additional funds to:

     .    Finance unanticipated working capital requirements;

     .    Pay for increased operating expenses or shortfalls in anticipated
          revenues;

     .    Fund increases in research and related expenditures;

     .    Develop new technology, products or services;

     .    Acquire rights to new products;

     .    Respond to competitive pressures; and

     .    Support strategic and industry relationships.

     There is no assurance that additional financing will be available on terms
acceptable to us, or at all. If adequate funds are not available to us then we
may not be able to continue operations or take advantage of opportunities, or we
may have to downsize our operations. If CECO raises additional equity funds, the
percentage ownership of our stockholders will be reduced.

Future Sales By Our Stockholders May Adversely Affect Our Stock Price And Our
Ability To Raise Funds In New Stock Offerings

     The selling stockholders intend to sell in the public market the shares of
common stock being registered in this offering. Such sales may cause our stock
price to decline. Sales may also make it more difficult for us to sell equity
securities or equity-related securities in the future at a time and price that
our management deems acceptable or at all. In addition, under the Subscription
Agreement we entered into with each of the Investors, we are required to issue
to such Investors additional shares based on an earnings formula (as set forth
in the Subscription Agreement executed in connection with the issuance of the
Investor Shares) for fiscal year 2002, up to a maximum of 826,802 additional
shares. Based on the results of this formula, 382,237 additional shares were
issued to the Investors as of April 28, 2003. In addition, Phillip DeZwirek has
warrants to purchase 2,250,000 shares of CECO common stock, which shares we are
obligated to register upon demand. Should Mr. DeZwirek elect to sell such
shares, such sales may cause our stock price to decline.

Risks Related To This Offering

        A large number of shares of our common stock will become available
for sale in the future, which may adversely affect the market price of our
common stock.

                                        5



                The market price of our common stock could decline as a result
of sales of a large number of shares in the market after this offering or the
perception that these sales could occur. These factors also could make it more
difficult for us to raise funds through future offerings of our common stock.

                As of the date of this Prospectus, there are 9,971,973 shares of
common stock outstanding, 9,589,736 of which will be freely transferable without
restriction or further registration under the Securities Act.

                Phillip DeZwirek, holder of warrants to purchase 2,250,000
shares of common stock, has registration rights with respect to all of such
shares. If those registration rights are exercised, shares covered by a
registration statement can be sold in the public market. Additionally, shares
issued upon exercise of stock options issued under our stock option plan will be
eligible for resale in the public market without restriction, which could
adversely affect our stock price. Shares issued upon the exercise of other
options and warrants could also occur, subject to limitations under Rule 144 of
the Securities Act. In addition, under the Subscription Agreement we entered
into with each of the Investors, we are required to issue to such Investors
additional shares based on an earnings formula (as set forth in the Subscription
Agreement executed in connection with the issuance of the Investor Shares) for
fiscal year 2002, up to a maximum of 826,802 additional shares. Based on the
results of this formula, 382,237 additional shares were issued to the investors.

                The market price of our common stock is highly volatile and may
decline. Factors that could cause fluctuation in our stock price may include,
among other things:

        .   actual or anticipated variations in quarterly operating results;

        .   an economic downturn in the manufacturing sector;

        .   announcements or cancellations of orders;

        .   changes in financial estimates by securities analysts;

        .   conditions or trends in our industry;

        .   changes in the market valuations of other companies in our industry;

        .   the effectiveness and commercial viability of products offered by us
            or our competitors;

        .   the results of our research and development;

        .   announcements by us or our competitors of technological innovations,
            new products, significant acquisitions, strategic partnerships,
            divestitures, joint ventures or other strategic initiatives;

                                        6



        .   additions or departures of key personnel; and

        .   sales of our common stock.

                Many of these factors are beyond our control. These factors may
cause the market price of our common stock to decline, regardless of our
operating performance. In addition, stock markets have experienced extreme price
volatility in recent years. This volatility has had a substantial effect on the
market prices of securities issued by many companies for reasons that may be
unrelated to the operating performance of the specific companies. These broad
market fluctuations may adversely affect the market price of our common stock.

                                 USE OF PROCEEDS

                This Prospectus is part of a registration statement that permits
selling shareholders to sell their shares. Because this Prospectus is solely for
the purpose of selling shareholders, we will not receive any proceeds from the
sale of stock being offered. If Warrant holders exercise their right to acquire
common shares, we could receive proceeds of $1,314,002, which would be used for
working capital purposes.

                              SELLING STOCKHOLDERS

                The following table sets forth the selling stockholders, and the
number of shares of common stock owned beneficially by them as of March 31,
2003, which may be offered pursuant to this Prospectus. This information is
based upon information provided to us by either the named selling stockholder or
our transfer agent. Because the selling stockholders may offer all, some or none
of their respective shares of common stock, no definitive estimate as to the
number of shares thereof that will be held by the selling stockholders after
such offering can be provided. The term "selling stockholder" includes the
stockholders listed below and their transferees, pledges, donees or other
successors. Except as set forth in the table below, none of the selling
stockholders is currently an affiliate of CECO, and none of them has had a
material relationship with us during the past three years.

                Percentage beneficial ownership is based on 9,971,973 shares of
common stock outstanding, as of April 30, 2003. Beneficial ownership is
calculated based on SEC requirements. All shares of the common stock subject to
options and warrants, including the Warrants, are deemed to be outstanding for
the purpose of computing the percentage of ownership of the person holding such
option or Warrants, but are not deemed to be outstanding for computing the
percentage of ownership of any other person.

                                        7





                                                  Shares Beneficially                              Shares Beneficially
                                                      Owned Before            Number of               Owned After
                                                        Offering               Shares                  Offering
Selling Stockholders/1/                         Number         Percent      Being Offered       Number/2/       Percent
----------------------------------              -------        --------     -------------       ---------       --------
                                                                                                     
Can-Med Technology, Inc./3/
d/b/a Green Diamond Oil Corp.
505 University Avenue, Suite 1400
Toronto, Ontario M5G 1X3                        800,000            8.0%           800,000               0              *

Crestview Capital Fund, L.P./4/
95 Revere Drive, Suite F
Northbrook, IL  60062                           840,042            8.2%           605,651         234,391           2.3%

Harvey Sandler /5/
17591 Lake Estates Drive
Boca Raton, FL  33496                           511,000            5.1%           100,000         411,000           4.1%

Robert Geras /6/
2125 Valley Road
Northbrook, IL 60062                            285,726            2.8%           210,000          75,726           0.7%

ICS Trustee Services, Ltd.
Nine Queens Road, Suite 605-6
Central, Hong Kong                              100,000            1.0%           100,000               0              *

Steven Erlbaum /7/
42 W. Lancaster, 2nd Floor
Ardmore, PA 19003                               102,045            1.0%            75,000          27,045              *


Erlbaum Family L.P./8/
42 W. Lancaster, 2nd Floor
Ardmore, PA 19003                               102,045            1.0%            75,000          27,045              *


Friedman Investment Group, LLC/9/
4250 W. Chase Avenue
Lincolnwood, IL 60712                            68,031            0.7%            50,001          18,030              *


Gary J. Shemano /10/
c/o The Shemano Group, Inc.
601 California Street, Suite 1150
San Francisco, CA 94108                           5,180               *             5,180               0              *



                                        8




                                                                                                     
Michael Jacks /10/
c/o The Shemano Group, Inc.
601 California Street, Suite 1150
San Francisco, CA 94108                           4,200               *             4,200               0              *

Bill and Mary Corbett /10/
c/o The Shemano Group, Inc.
601 California Street, Suite 1150
San Francisco, CA 94108                           2,100               *             2,100               0              *

Brian Mikes /10/
c/o The Shemano Group, Inc.
601 California Street, Suite 1150
San Francisco, CA 94108                           2,100               *             2,100               0              *

Jim Keener /10/
c/o The Shemano Group, Inc.
601 California Street, Suite 1150
San Francisco, CA 94108                             420               *               420               0              *


*      Less than 1%

----------
/1/  To our knowledge and except as otherwise set forth herein, the selling
     stockholders have sole voting and investment power with respect to all
     common stock shown as beneficially owned by them, subject to community
     property laws where applicable. Except as otherwise set forth herein, the
     table includes shares of common stock that the selling stockholders have
     the right to acquire pursuant to the exercise of warrants and options
     exercisable within 60 days.
/2/  Percentage ownership is based on 9,971,973 shares of common stock
     outstanding as of April 30, 2003 and, except as otherwise set forth herein,
     in each case assumes exercise of warrants and options.
/3/  50.1% of the shares of Green Diamond are owned by Icarus Investment Corp.
     ("Icarus"). Icarus is owned 50% by Phillip DeZwirek and 50% by Jason Louis
     DeZwirek. Phillip DeZwirek is Chief Executive Officer and Chairman of the
     Board of CECO, and Jason Louis DeZwirek is Secretary of CECO. Icarus has
     voting and dispositive power, with respect to such shares, which is shared
     with the other shareholders of Green Diamond. Jason Louis DeZwirek is the
     son of Phillip DeZwirek.
/4/  The number of shares of common stock listed includes the shares of common
     stock issuable upon exercise of the Warrants held by Crestview Capital
     Fund, L.P. for 216,667 shares of common stock. Crestview Capital Fund, L.P.
     previously sold 44,350 shares of stock under the registration statement.
/5/  Includes 20,000 shares held in the name of Phyllis Sandler, the spouse of
     Mr. Sandler.
/6/  The number of shares of common stock listed includes the shares of common
     stock issuable upon exercise of the Warrants held by Mr. Geras for 70,000
     shares of common stock.
/7/  The number of shares of common stock listed includes the shares of common
     stock issuable upon exercise of the Warrants held by Mr. Erlbaum for 25,000
     shares of common stock.
/8/  The number of shares of common stock listed includes the shares of common
     stock issuable upon exercise of the Warrants held by the Erlbaum Family
     L.P. for 25,000 shares of common stock.
/9/  The number of shares of common stock listed includes the shares of common
     stock issuable upon exercise of the Warrants held by Friedman Investment
     Group, LLC for 16,667 shares of common stock.
/10/ All of the number of shares of common stock listed are shares of common
     stock issuable upon exercise of Warrants held by such party.

                                        9



                              PLAN OF DISTRIBUTION

        The selling stockholders and any of their pledges, assignees and
successors-in-interest may, from time to time, sell any or all of their shares
of common stock on any stock exchange, market or trading facility on which the
shares are traded or in private transactions. These sales may be at fixed or
negotiated prices. Subject to contractual limitations, the selling stockholders
may use any one or more of the following methods when selling shares:

        .       ordinary brokerage transactions in which the broker-dealer
                solicits purchasers;

        .       block trades in which the broker-dealer will attempt to sell the
                shares as agent but may position and resell a portion of the
                block as principal to facilitate the transaction;

        .       purchases by a broker-dealer as principal and resale by the
                broker-dealer for its account;

        .       an exchange distribution in accordance with the rules of the
                applicable exchange;

        .       privately negotiated transactions;

        .       short sales;

        .       broker-dealers may agree with the selling stockholders to sell a
                specified number of such shares at a stipulated price per share;

        .       a combination of any such methods of sale; and

        .       any other method permitted pursuant to applicable law.

        The selling stockholders also may sell shares under Rule 144 of the
Securities Act of 1933, if available, rather than under this prospectus.

        The selling stockholders may pledge their shares to their brokers under
the margin provisions of customer agreements. If a selling stockholder defaults
on a margin loan, the broker may, from time to time, offer and sell the pledged
shares.

        In order to comply with the securities laws of certain states, if
applicable, the shares may be sold only through registered or licensed brokers
or dealers. In addition, in certain states, the shares may not be sold unless
they have been registered or qualified for sale in the state or an exemption
from the registration or qualification requirement is available and complied
with.

        Brokers, dealers, underwriters, or agents participating in the
distribution of the shares as agents may receive compensation in the form of
commissions, discounts, or concessions from the selling stockholders and/or
purchasers of the common stock for whom the broker-dealers

                                       10



may act as agent, or to whom they may sell as principal, or both. The
compensation paid to a particular broker-dealer may be less than or in excess of
customary commissions, however, the maximum commission or discount to be
received by any NASD member or independent broker-dealer will not be greater
than eight (8) percent for the sale of any securities being registered hereunder
pursuant to Rule 415 of the Securities Act.

        Crestview Capital Fund L.P. is an affiliate of, by virtue of being under
common control with, Dillon Capital, Inc., a registered broker-dealer. Crestview
Capital Fund L.P. purchased its shares and Warrants in the ordinary course of
business, and at the time of the purchase of such shares and Warrants had no
agreements or understandings, directly or indirectly, with any person to
distribute the shares or Warrants.

        Green Diamond is an "underwriter" within the meaning of Section 2(11) of
the Securities Act. A majority of the shares of Green Diamond (50.1%) are owned
by Icarus Investment Corp., which is owned 50% by Phillip DeZwirek and 50% by
Jason DeZwirek, both of whom are officers and directors of the Company. Green
Diamond is not directly or indirectly affiliated or associated with an NASD
member.

        Neither we nor the selling stockholders can presently estimate the
amount of compensation that any agent will receive. We know of no existing
arrangements between any selling stockholders, any other stockholders, broker,
dealer, underwriter, or agent relating to the sale or distribution of the
shares. At the time a particular offer of shares is made, a prospectus
supplement, if required, will be distributed that will set forth the names of
any agents, underwriters, or dealers and any compensation from the selling
stockholders and any other required information.

        We will pay all of the expenses incident to the registration, offering,
and sale of the shares for the public other than commissions or discounts of
underwriters, broker-dealers, or agents. We have also agreed to indemnify the
selling shareholders against specified liabilities, including liabilities under
the Securities Act.

        Insofar as indemnification for liabilities arising under the Securities
Act, as amended, may be permitted to our directors, officers, and controlling
persons, we have been informed that in the opinion of the SEC this
indemnification is against public policy as expressed in the Securities Act and,
therefore, is unenforceable.

        We have advised the selling stockholders that while they are engaged in
a distribution of the shares included in this Prospectus they are required to
comply with Regulation M promulgated under the Securities Exchange Act of 1934,
as amended. With certain exceptions, Regulation M precludes the selling
stockholders, any affiliated purchasers, and any broker-dealer or other person
who participates in the distribution from bidding for or purchasing, or
attempting to induce any person to bid for or purchase any security which is the
subject of the distribution until the entire distribution is complete.
Regulation M also prohibits any bids or purchases made in order to stabilize the
price of a security in connection with the distribution of that security. All of
the foregoing may affect the marketability of the shares offered hereby this
Prospectus.

                                       11



        This offering will terminate on the earlier of (i) the date that all
shares offered by this Prospectus have been sold by the selling shareholders,
(ii) November 15, 2003, or (iii) the date all of the selling shareholders may
sell all of the shares described herein without restriction by the volume
limitations of Rule 144(k) of the Securities Act. However, with respect to the
shares held by Green Diamond, Harvey Sandler and ICS Trustee Services, Ltd.,
this offering will not terminate until the earlier of when such parties have
sold their shares or December 5, 2010.

                                  LEGAL MATTERS

        The validity of the common stock offered will be passed upon for CECO by
Sugar, Friedberg & Felsenthal, 30 N. LaSalle Street, Suite 3000, Chicago,
Illinois 60602.

                                     EXPERTS

        The consolidated financial statements of CECO at December 31, 2002,
incorporated by reference in this Prospectus, have been audited by Deloitte &
Touche LLP, Certified Public Accountants, independent auditors, as set forth in
its report thereon, which is incorporated by reference herein. The financial
statements are included in reliance upon such reports given upon the authority
of such firm as experts in accounting and auditing.

                                       12



                       WHERE YOU CAN GET MORE INFORMATION

        We have filed with the Securities and Exchange Commission a Registration
Statement under the Securities Act, with respect to the shares offered hereby.
This prospectus is part of the registration statement. This prospectus does not
contain all the information set forth in the registration statement and the
exhibits and schedules thereto, to which reference is hereby made for further
information. This prospectus does not contain all the information included in a
registration statement because we have omitted parts of the registration
statement as permitted by the SEC's rules and regulations. For further
information about us, you should refer to the registration statement. Statements
contained in this prospectus as to any contract, agreement or other document
referred to are not necessarily complete. Where the contract or other document
is an exhibit to the registration statement, each statement is qualified by the
provisions of that exhibit.

        We are a reporting company and also file annual, quarterly and current
reports, proxy statements and other information with the Securities and Exchange
Commission. You may inspect and copy all or any portion of the registration
statement or any reports, proxy statements, or other information at the
Securities and Exchange Commission's Public Reference Room at 450 Fifth Street,
N.W., Washington, D.C. 20549. You can request copies of these documents by
writing to the Securities and Exchange Commission and paying a fee for the
copying cost. Please call the Securities and Exchange Commission at
1-800-SEC-0330 for more information about the operation of the public reference
rooms. In addition, such information may be accessed electronically at the
Securities and Exchange Commission's web site on the Internet at www.sec.gov.

        The Securities and Exchange Commission allows us to "incorporate by
reference" information that we file with them, which means that we can disclose
important information to you by referring you to those documents. The
information incorporated by reference is an important part of this prospectus,
and information that we file later with the Securities and Exchange Commission
will automatically update and supersede this information. We incorporate by
reference the documents listed below and any future filings we will make with
the Securities and Exchange Commission under Sections 13(a), 13(c), 14 or 15(d)
of the Securities Exchange Act of 1934 until our offering is completed:

        .       Annual Report on Form 10-K for the year ended December 31, 2002;
                and

        .       The description of our common stock contained in the
                registration statement on Form 10 filed with the Securities and
                Exchange Commission on December 13, 1992 pursuant to Section
                12(g) of the Securities Exchange Act of 1934, together with all
                amendments or reports filed for the purpose of updating such
                description.

        We will provide to each person to whom a Prospectus is delivered,
including any beneficial owner, a copy of these filings at no cost, upon written
or oral request at the following address or telephone number:

                CECO Environmental Corp.
                Attn: Marshall J. Morris
                5120 Forrer Street
                Cincinnati, Ohio 45209
                (513) 458-2600

                                       13




        THIS PROSPECTUS IS PART OF A LARGER REGISTRATION STATEMENT WE FILED WITH
THE SECURITIES AND EXCHANGE COMMISSION. YOU SHOULD RELY ONLY ON THE INFORMATION
INCORPORATED BY REFERENCE OR PROVIDED IN THIS PROSPECTUS. WE HAVE NOT AUTHORIZED
ANYONE ELSE TO PROVIDE YOU WITH DIFFERENT INFORMATION. WE ARE NOT MAKING AN
OFFER OF THESE SECURITIES IN ANY STATE WHERE THE OFFER IS NOT PERMITTED. YOU
SHOULD NOT ASSUME THAT THE INFORMATION IN THIS PROSPECTUS IS ACCURATE AS OF ANY
OTHER DATE OTHER THAN THE DATE ON THE FRONT OF THE DOCUMENT.

No dealer, sales representative or any
other person has been authorized to give
any information or to make any
representations in connection with this
offering other than those contained in                   2,074,002 Shares
this prospectus, and, if given or made,
such information or representations must
not be relied upon as having been
authorized by the Company or any of the               CECO Environmental Corp.
Selling Stockholders. This prospectus
does not constitute an offer to sell, or
a solicitation of an offer to buy, any
securities to which it relates or an                       Common Stock
offer to, or a solicitation of, any
person in any jurisdiction where such
offer or solicitation would be unlawful.
Neither the delivery of this prospectus
nor any sale made hereunder shall, under
any circumstances, create any
implication that there has been no
change in the affairs of the Company
since the date hereof or that the
information contained herein is correct             -------------------------
as of any time subsequent to the date                       Prospectus
hereof.

                                                           April 30, 2003

                  TABLE OF CONTENTS

Overview......................................................1
Risk Factors..................................................2
Use of Proceeds...............................................7
Selling Shareholders..........................................7
Plan of Distribution.........................................10
Legal Matters................................................12
Experts......................................................12
Where You Can Find More Information..........................13





              PART II - INFORMATION NOT REQUIRED IN THE PROSPECTUS

ITEM 14.     OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION*

        The following is a statement of estimated expenses of the issuance and
distribution of the securities being registered (other than underwriting
discounts and commissions), all of which are being paid by the Registrant"

            SEC Registration Fee......................           $      725.07
            NASD Filing Fee...........................                1,288.12
            Accountant's Fees and Expenses............               60,000.00
            Legal Fees and Expenses...................              175,000.00
            Printing Expenses.........................               15,000.00
            Blue Sky Qualification Fees and Expenses..                1,000.00
            Miscellaneous.............................               10,000.00
                     Total............................           $  263,013.19

                *All amounts are estimates except for the SEC Registration Fee
                and the Nasdaq Listing Fee.

ITEM 15.     INDEMNIFICATION OF DIRECTORS AND OFFICERS

        Under Section 145 of the Delaware General Corporation Law, our
certificate of incorporation and our bylaws provide for indemnification of our
directors, officers, employees and other agents to the extent permitted by the
Delaware General Corporation Law. Mandatory indemnification is required for
directors and executive officers, and we provide for permissive indemnification
for other officers, employees and agents. Also, we are authorized to purchase
insurance on behalf of an individual for liabilities incurred whether or not we
would have the power or obligation to indemnify him under our bylaws.

ITEM 16.     EXHIBITS

4.1     CECO Filters, Inc. Savings and Retirement Plan. (Incorporated by
reference from CECO's Annual Report on Form 10-K for the fiscal year ended
December 31, 1990)

4.2     CECO Environmental Corp. 1997 Stock Option Plan and Amendment.
(Incorporated by reference from Form S-8, Exhibit 4, filed March 24, 2000, of
the Company)

4.3     1999 CECO Environmental Corp. Employee Stock Purchase Plan.
(Incorporated by reference from Form S-8, filed September 22, 1999 of the
Company)

4.4     Form of Warrant (for Investors). (Incorporated by reference from the
Company's Form 8-K filed January 15, 2002)

                                      II-1



4.5     Form of Warrant (for Finders). (Incorporated by reference from Form 10-K
dated December 31, 2001)

5.1*    Opinion of Sugar Friedberg & Felsenthal.

24.1*   Power of Attorney (see Page II-4).

         * Filed herewith.

ITEM 17.     UNDERTAKINGS

        (a)     The undersigned Registrant hereby undertakes:

                (i)     to file, during any period in which offers or sales are
being made, a post-effective amendment to this registration statement:

                (A)     to include any material information with respect to the
plan of distribution not previously disclosed in the registration statement or
any material change to such information in the registration statement;

                (B)    that, for purposes of determining any liability under
the Securities Act of 1933, each such post-effective amendment shall be deemed
to be a new registration statement relating to the securities offered therein,
and the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof, and

                (C)   to remove from registration by means of a post effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

        (b)     The undersigned Registrant hereby undertakes that, for purposes
of determining any liability under the Securities Act of 1933, each filing of
the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in this
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

        (c)     Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Securities Act of 1933 and is, therefore, unenforceable. In the event
that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has

                                      II-2



been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act of 1933 and will be governed by the
final adjudication of such issue.

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the city of Boca Raton, State of Florida on April 30, 2003.

                                                CECO Environmental Corp.

                                                By:    /s/ Phillip DeZwirek
                                                   -----------------------------
                                                   Phillip DeZwirek
                                                   Chief Executive Officer

                                      II-3



                                POWER OF ATTORNEY

        KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints the Chairman and Chief Executive Officer, the
Chief Financial Officer, or any of them, as his true and lawful
attorneys-in-fact and agents, with full power of substitution and
resubstitution, for him and in his name, place and stead in any and all
capacities, to sign any or all amendments to this Registration Statement
(including post-effective amendments), and to file the same, with all exhibits
thereto, and other documents in connection therewith with the Securities and
Exchange Commission, granting unto said attorneys-in-fact and agents full power
and authority to do and perform each and every act and thing requisite and
necessary to be done in and about the premises, as fully and to all intents and
purposes as he might or could do in person, hereby ratifying and confirming that
said attorneys-in-fact and agents, or their substitute or substitutes, may
lawfully do or cause to be done by virtue hereof.

        Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the following
capacities on April 30, 2003.


/s/ Phillip DeZwirek
------------------------------              April 30, 2003
Phillip DeZwirek, Chairman
of the Board, Director and
Chief Executive Officer
(Principal Executive Officer)


/s/ Marshall J. Morris
------------------------------              April 30, 2003
Marshall J. Morris,
Vice President-Finance
and Administration;
Chief Financial Officer
(Principal Accounting and
Financial Officer)

/s/ Richard J. Blum
------------------------------              April 30, 2003
Richard J. Blum, President,
Director


/s/ Jason Louis DeZwirek
------------------------------              April 30, 2003
Jason Louis DeZwirek, Director

/s/ Josephine Grivas
------------------------------              April 30, 2003
Josephine Grivas, Director

                                      II-4