SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                 AMENDMENT NO. 3


                                       to

                                    FORM 20-F

(Mark One)

|X|   REGISTRATION STATEMENT PURSUANT TO SECTION 12(b) OR (g) OF THE SECURITIES
      EXCHANGE ACT OF 1934

OR

|_|   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
      ACT OF 1934

OR

|_|   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934

For the transition period from _________________ to ________________

                         Commission file number: 0-49984

                           MITEL NETWORKS CORPORATION
             (Exact name of Registrant as specified in its charter)

                                     Canada
                 (Jurisdiction of incorporation or organization)

                                350 Legget Drive
                         Ottawa, Ontario, Canada K2K 2W7
                    (Address of principal executive offices)

Securities registered or to be registered pursuant to Section 12(b) of the Act:
None

Securities registered or to be registered pursuant to Section 12(g) of the Act:

                         Common Shares Without Par Value
                                (Title of Class)

Securities for which there is a reporting obligation pursuant to Section 15(d)
of the Act: None


Indicate the number of outstanding shares of each of the issuer's classes of
capital or common stock as of the close of the period covered by the annual
report: 115,446,964 common shares as of January 26, 2003


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.                           Yes |_|  No |X|

Indicate by check mark which financial statement item the registrant has elected
to follow.

Item 17 |_|  Item 18 |X|
<PAGE>



Item 19. Exhibits

1.    Articles of Incorporation and bylaws as currently in effect:

      1.1   Articles of Incorporation and related amendments*

      1.2   Bylaws*

2.    Instruments defining the rights of holders of equity securities being
      registered:

      2.1   See Articles of Incorporation described above in Exhibit 1.1

      2.2   Specimen Common Share certificate*

4.    Material contracts:

      4.1   Amended and Restated Shareholders' Agreement between Mitel Networks
            Corporation, Mitel Systems Corporation, Zarlink Semiconductor Inc.
            and Power Technology Investment Corporation dated August 31, 2002*

      4.2   Subscription Agreement between Mitel Networks Corporation and Power
            Technology Investment Corporation dated August 31, 2001 and related
            amendment No. 1 dated May 3, 2002*

      4.3   Amended and Restated Loan Agreement between Mitel Networks
            Corporation, the Lenders from time to time and Bank of Montreal as
            Administrative Agent dated January 21, 2002*

      4.4   Chattel Mortgage Loan Agreement between Mitel Networks Limited and
            Barclays Bank PLC dated October 22, 2001*

      4.5   Real Property Loan Facility between Mitel Networks Limited and
            Barclays Bank PLC dated December 13, 2001, secured by a legal charge
            dated January 24, 2002*

      4.6   Business Overdraft and Ancillary Facility Agreement between Mitel
            Networks Limited and Barclays Bank PLC dated June 24, 2002*

      4.7   Business Overdraft and Ancillary Facility Agreements between Mitel
            Networks Limited and Lloyd's TSB Bank PLC dated October 8, 2001 and
            March 11, 2002*

      4.8   Promissory notes receivable and promissory notes payable between
            Mitel Networks Corporation, Mitel Networks, Inc., Mitel Networks
            Limited, BreconRidge Manufacturing Solutions Limited, BreconRidge
            Manufacturing Solutions Inc. and BreconRidge Manufacturing Solutions
            Limited dated August 31, 2001*



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<PAGE>

      4.9   Supply Agreement between Mitel Networks Corporation and its
            subsidiaries and Ridgeway Research Corporation and its subsidiaries
            dated August 30, 2001* +

      4.10  Sublease Agreement between Mitel Networks Corporation and Ridgeway
            Research Corporation dated August 31, 2001 and First Amendment of
            Sublease Agreement between Mitel Networks Corporation and Ridgeway
            Research Corporation (now known as BreconRidge Manufacturing
            Solutions Corporation) dated May 31, 2002*

      4.11  Lease Agreement between Mitel Networks Limited and BreconRidge
            Manufacturing Solutions Limited dated September 14, 2001*

      4.12  Asset Sale Agreement between Mitel Networks Corporation and Ridgeway
            Research Corporation dated August 31, 2001*

      4.13  Asset Sale Agreement between Mitel Networks Limited and BreconRidge
            Manufacturing Solutions Limited dated August 31, 2001* +

      4.14  Asset Sale Agreement between Mitel Networks, Inc. and BreconRidge
            Manufacturing Solutions, Inc. dated August 31, 2001*

      4.15  Promissory Note between Mitel Networks Corporation and Mitel
            Knowledge Corporation dated December 21, 2001*

      4.16  Research and Development Agreement between Mitel Networks
            Corporation and Mitel Knowledge Corporation dated March 27, 2001 and
            related addendum No. 1 dated November 23, 2001*

      4.17  Research and Development Cost-sharing Agreement between Mitel
            Networks Overseas Limited, then known as Mitel Networks (Barbados)
            Limited, a subsidiary of Mitel Networks Corporation, and Mitel
            Knowledge Corporation dated March 27, 2001*

      4.18  Intellectual Property License Agreement between Mitel Networks
            Overseas Limited, then known as Mitel Networks (Barbados) Limited, a
            subsidiary of Mitel Networks Corporation, and Mitel Knowledge
            Corporation dated March 27, 2001*

      4.19  Assignment and Assumption Agreement between Mitel Networks Overseas
            Limited, then known as Mitel Networks (Barbados) Limited, Mitel
            Networks Corporation and Mitel Knowledge Corporation dated March 27,
            2001*

      4.20  Assignment and Assumption Agreement between Mitel Networks
            Corporation and Mitel Knowledge Corporation dated February 16, 2001*



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<PAGE>

      4.21  Acquisition by Mitel Networks, Inc. and Mitel Networks Limited of
            preferred shares in Mitel Knowledge Corporation in February 2001 and
            March 2001*

      4.22  Acquisition Agreement by and between Mitel Corporation (now known as
            Zarlink Semiconductor Inc.), 3755461 Canada Inc. (now known as Mitel
            Systems Corporation) and Dr. Terence H. Matthews ("Acquisition
            Agreement"), dated January 2, 2001.*

            The following exhibits to the Acquisition Agreement have been
            omitted. Mitel Networks Corporation will furnish supplementally a
            copy of any omitted schedule to the Securities and Exchange
            Commission upon request:

            Schedule 1.1(nn) Financial Statements Schedule
            Schedule 1.1(nnn) Permitted Encumbrances
            Schedule 2.2 Purchase Price Allocation Schedule
            Schedule 2.3 Audit Report Schedule
            Schedule 3.4 Authorized and Issued Capital - Vendor Group
            Schedule 3.6 Loan Agreement Particulars
            Schedule 3.7 Vendor Group Subsidiaries
            Schedule 3.8 Violations
            Schedule 3.9 Locations
            Schedule 3.11 Real and Leased Property
            Schedule 3.13 Real Property Leases
            Schedule 3.16(a)-(g) Business Intellectual Property
            Schedule 3.19 Material Contracts
            Schedule 3.20 Licenses and Permits
            Schedule 3.21 Consents
            Schedule 3.25 Tax Matters
            Schedule 3.26 Legal and Regulatory Proceedings
            Schedule 3.28 Environmental Matters
            Schedule 3.29 Employee Plans Excluding United States
            Schedule 3.30 Employee Benefit Plans - United States
            Schedule 3.31 Collective Agreements
            Schedule 3.32 Employees and Contractors
            Schedule 3.34 Customers and Suppliers
            Schedule 3.35 Product Warranties
            Schedule 3.36 Grants
            Schedule 6.1(a) Restructuring
            Schedule 6.2(a) Current Corporate Structure
            Schedule 6.2(b) Reorganization
            Schedule 6.2(d)(i) Lease Agreement
            Schedule 6.2(d)(ii) Phase V Lease
            Schedule 6.2(e) License Agreement
            Schedule 6.3(a) Transition Plan Agreement
            Schedule 6.11 Non-Competition Agreement
            Schedule 6.22 Employees



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<PAGE>

            Schedule 6.23 Tangible Personal Property
            Schedule 7.1(i) Form of Opinion of Vendor's Counsel
                            (Canada, UK and US)
            Schedule 7.1(m) Supply Agreement
            Schedule 7.1(n) Shareholders Agreement
            Schedule 7.1(p) Form of Release
            Schedule 7.3(f) Form of Opinion of Purchaser's Counsel

      4.23  Supply Agreement between Mitel Networks Corporation and Mitel
            Corporation (now known as Zarlink Semiconductor Inc.) dated February
            16, 2001 and related amendment dated October 24, 2001* +

      4.24  Lease Agreement between Mitel Networks Limited and Mitel
            Semiconductor Limited, a subsidiary of Zarlink Semiconductor Inc.
            dated February 2, 2001*

      4.25  Intellectual Property License Agreement between Mitel Networks
            Corporation and Mitel Corporation (now known as Zarlink
            Semiconductor Inc.) dated February 16, 2001* +

      4.26  Amendment to the Intellectual Property License Agreement between
            Mitel Networks Corporation and Zarlink Semiconductor Inc. dated
            October 24, 2001*

      4.27  Patent Sub-License Agreement between Mitel Networks Corporation and
            Mitel Corporation (now known as Zarlink Semiconductor Inc.) dated
            February 16, 2001 under which Mitel Corporation (now known as
            Zarlink Semiconductor Inc.) licenses certain rights under a Patent
            License Agreement with Lucent Technologies Inc. dated April 1, 1998*
            +

      4.28  Non Competition and Non Solicitation Agreement between Mitel
            Corporation (now known as Zarlink Semiconductor Inc.), Mitel
            Semiconductor V.N. Inc., Mitel Semiconductor Limited, Mitel
            Semiconductor Inc., 3755461 Canada Inc., Mitel Networks Corporation
            and Mitel Research Park Corporation dated February 16, 2001*

      4.29  Promissory Notes between Mitel Networks Corporation and Wesley
            Clover Corporation, formerly 10750 Newfoundland Limited, dated
            between April 22, 2002 and July 25, 2002*

      4.30  Lease Agreement between Mitel Networks Corporation and Mitel
            Research Park Corporation dated March 27, 2001*

      4.31  Strategic Alliance Agreement between Mitel Networks Corporation and
            March Networks Corporation dated September 21, 2001*

      4.32  Global Distribution Agreement between Mitel Networks Corporation and
            March Networks Corporation dated February 15, 2002* +



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<PAGE>

      4.33  Amended and Restated Employment Contract between Mitel Networks
            Corporation and Donald Smith dated April 17, 2001* +

      4.34  Amended and Restated Employment Contract between Mitel Networks
            Corporation and Paul Butcher dated February 16, 2001* +

      4.35  Union Agreement between Mitel Communications Solutions, Inc. (now
            known as Mitel Networks Solutions, Inc.) and International
            Brotherhood of Electrical Workers Union expiring on September 30,
            2003* +

      4.36  Integrated Communications Solutions R&D Project Agreement between
            Mitel Networks Corporation, Mitel Knowledge Corporation, March
            Networks Corporation and Her Majesty the Queen in Right of Canada
            dated October 10, 2002 +

      8.1   Subsidiaries of Mitel Networks Corporation*

----------
*     Previously filed as part of this Registration Statement.

+     Portions of this document have been submitted to the Secretary of the
      Securities and Exchange Commission for application for "Confidential
      Treatment."



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<PAGE>



                                    SIGNATURE

      The registrant hereby certifies that it meets all of the requirements for
filing on Form 20-F and that it has duly caused and authorized the undersigned
to sign this registration statement on its behalf.

                                                 MITEL NETWORKS CORPORATION

                                                 /s/ DONALD W. SMITH
                                                 -------------------------------
                                                 Name:  Donald W. Smith
                                                 Title:  Chief Executive Officer


Date: February 11, 2003

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