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UNITED STATESSECURITIES
AND EXCHANGE COMMISSIONWashington, D.C. 20549

FORM 40-F

(Check One)

[_] Registration statement pursuant to Section 12 of the
Securities Exchange Act of 1934

or

[X] Annual report pursuant to section 13(a) or 15(d) of the
Securities Exchange Act of 1934

For the fiscal year ended December 31, 2014

Commission file number1-36596

TRILLIUM THERAPEUTICS INC.(Exact
name of registrant as specified in its charter)

|Ontario, Canada                    | 2834                         | Not applicable                        
|---------------------------------- | ---------------------------- | --------------------------------------
|(Province or other jurisdiction of | (Primary Standard Industrial | (I.R.S. Employer                      
|incorporation or organization)     | Classification Code Number   | Identification Number (if applicable))
|                                   | (if applicable))             |                                       

96 Skyway Avenue, Toronto, Ontario, Canada M9W 4Y9
Telephone: (416) 595-0627(Address and Telephone Number of
Registrants Principal Executive Offices)

Puglisi & Associates, 850 Library Avenue, Suite 204,
Newark, Delaware 19711 Telephone: (302) 738-6680(Name, Address
(Including Zip Code) and Telephone Number (Including Area Code) of Agent For
Service in the United States)

Securities registered or to be registered pursuant to Section
12(b) of the Act.

|Title of each class | Name of each exchange on which
      registered
|------------------- | -----------------------------------------------
|Common Shares       | The NASDAQ Stock Market LLC                    

Securities registered or to be registered pursuant to Section
12(g) of the Act. None

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

For annual reports, indicate by check mark the information filed
with this Form:

|[X] Annual Information Form | [X] Audited Annual Financial Statements
|--------------------------- | ---------------------------------------

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: 4,427,244

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 (the Exchange Act) 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 [X]        No [_]

Indicate by check mark whether the registrant has submitted
electronically and posted on its corporate Web site, if any, every Interactive
Data File required to be submitted and posted pursuant to Rule 405 of Regulation
S-T (s.232.405 of this chapter) during the preceding 12 months (or for such
shorter period that the registrant was required to submit and post such files).

Yes [_]      No [_]

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FORM 40-F

Principal Documents

The following documents, filed as Exhibits 99.1, 99.2 and 99.3
to this Annual Report on Form 40-F, are hereby incorporated by reference into
this Annual Report on Form 40-F:

| | (a) | Annual Information Form for the fiscal year ended
      December 31, 2014 dated March 23, 2015;                                                                                                                                  
| | --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |     |                                                                                                                                                                                                                                  
| | (b) | Managements Discussion and Analysis for the years ended
      December 31, 2014 and 2013; and                                                                                                                                   
| |     |                                                                                                                                                                                                                                  
| | (c) | Audited Consolidated Financial Statements for the years
      ended December 31, 2014 and 2013, prepared under International Financial
      Reporting Standards as issued by the International Accounting Standards
      Board.

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ADDITIONAL DISCLOSURE

Certifications and Disclosure Regarding Controls and
Procedures.

|(a) | Certifications. See Exhibits 99.4, 99.5, 99.6 and
      99.7 to this Annual Report on Form 40-F.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|--- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|(b) | Disclosure Controls and Procedures. As of the end
      of Trillium Therapeutics Inc.s (Trillium) fiscal year ended December
      31, 2014, an evaluation of the effectiveness of Trilliums disclosure
      controls and procedures (as such term is defined in Rules 13a-15(e) and
      15d-15(e) under the Exchange Act) was carried out by the management of
      Trillium, with the participation of the President and Chief Executive
      Officer (CEO) and the Chief Financial Officer (CFO) of Trillium. Based
      upon that evaluation, the CEO and CFO have concluded that as of the end of
      that fiscal year, Trilliums disclosure controls and procedures were
      effective to ensure that information required to be disclosed by Trillium
      in reports that it files or submits under the Securities Exchange Act of
      1934, as amended, is (i) recorded, processed, summarized and reported
      within the time periods specified in Securities and Exchange Commission
      (the Commission) rules and forms and (ii) accumulated and communicated
      to the management of Trillium, including the CEO and CFO, to allow timely
      decisions regarding required disclosure.
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|    | It should be noted that while the CEO and CFO believe
      that Trilliums disclosure controls and procedures provide a reasonable
      level of assurance that they are effective, they do not expect that
      Trilliums disclosure controls and procedures or internal control over
      financial reporting will prevent all errors and fraud. A control system,
      no matter how well conceived or operated, can provide only reasonable, not
      absolute, assurance that the objectives of the control system are
    met.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|(c) | Managements Annual Report on Internal Control Over
      Financial Reporting.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|    | This annual report does not include a report of
      managements assessment regarding internal control over financial
      reporting or an attestation report of the companys registered public
      accounting firm due to a transition period established by rules of the
      Commission for newly public companies.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|(d) | Attestation Report of the Registered Public Accounting
      Firm.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|    | This annual report does not include a report of
      managements assessment regarding internal control over financial
      reporting or an attestation report of the companys registered public
      accounting firm due to a transition period established by rules of the
      Commission for newly public companies.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|(e) | Changes in Internal Control Over Financial
      Reporting. The required disclosure is included under the heading
      Disclosure Controls and Internal Controls Over Financial Reporting in Trilliums
Managements Discussion and Analysis for the years ended December 31, 2014 and
2013, filed as Exhibit 99.2 to this Annual Report on Form 40-F.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

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Notices Pursuant to Regulation BTR.

None.

Audit Committee Financial Expert.

Trilliums board of directors has determined that Luke Beshar,
a member of Trilliums audit committee, qualifies as an audit committee
financial expert (as such term is defined in Form 40-F) and is independent as
that term is defined in the rules of the Nasdaq Capital Market.

Code of Business Conduct.

Trillium has adopted a Code of Business Conduct and Ethics,
which qualifies as a code as ethics within the meaning of Form 40-F, that is
applicable to each of Trilliums directors, officers and employees, including
its principal executive officer, principal financial officer, principal
accounting officer or controller and persons performing similar functions.

The Code of Business Conduct and Ethics is available for
viewing on Trilliums website at www.trilliumtherapeutics.com, and is available in
print, without charge, to any shareholder who requests a copy of it. Requests
for copies of the Code of Business Conduct and Ethics should be made by
contacting: James Parsons, Chief Financial Officer by phone at (416) 595-0627 or
by e-mail to info@trilliumtherapeutics.com.

Since the date on which Trillium became subject to the
reporting requirements of Section 13(a) or 15(d) of the Exchange Act, there have
not been any amendments to, or waivers, including implicit waivers, granted
from, any provision of the Code of Business Conduct and Ethics.

If any amendment to the Code of Ethics is made, or if any
waiver from the provisions thereof is granted, Trillium may elect to disclose
the information about such amendment or waiver required by Form 40-F to be
disclosed, by posting such disclosure on its website, which may be accessed at
www.trilliumtherapeutics.com.

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Principal Accountant Fees and Services.

The following table provides information about the fees billed
to Trillium for professional services rendered by Ernst & Young LLP to
Trillium for the years ended December 31, 2014 and 2013:

|                      |    | Year ended December 31, | 
|--------------------- | -- | ----------------------- | 
|                      |    | 2014                    | 
|Audit fees(1)         | C$ | 313,820                 | 
|Audit-related fees(2) |    | -                       | 
|Tax fees(3)           |    | 2,050                   | 
|All other fees(4)     |    | -                       | 
|                      | C$ | 315,870                 | 

|(1) | Audit fees are the aggregate fees billed by Ernst &
      Young LLP for the audit of Trilliums consolidated annual financial
      statements, reviews of interim financial statements and attestation
      services that are provided in connection with statutory and regulatory
      filings or engagements. During 2014, the services also consisted of fees
      related to the filing of a base shelf prospectus and procedures for the
      Form 20-F filing. For 2013, the services consisted of fees related to
      incremental audit procedures related to the purchase price allocation of
      Trillium.
|--- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|(2) | Audit-related fees are fees charged by Ernst &
      Young LLP for assurance and related services that are reasonably related
      to the performance of the audit or review of the Trilliums financial
      statements and are not reported under Audit Fees.                                                                                                                                                                                                                                                                                                                                                         
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|(3) | Tax fees are fees billed by Ernst & Young LLP for
      tax compliance, tax advice and tax planning.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|(4) | All other fees are fees billed by Ernst & Young LLP
      for services not described above.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 

Pre-Approval Policies and Procedures.

|(a) | The audit committee of Trilliums board of directors has
      adopted an Auditor Services Pre-Approval Policy (the "Policy") with
      respect to the pre-approval of audit and permitted non-audit services to
      be provided by Ernst & Young LLP, Trilliums independent auditor.
      Pursuant to the Policy, the audit committee on an annual basis may approve
      the provision of a specified list of audit and permitted non-audit
      services that the audit committee believes to be typical, reoccurring or
      otherwise likely to be provided by the external auditor during the then
      current fiscal year. All pre-approvals granted under this Policy shall be
      sufficiently detailed as to the particular services being provided that it
      will not be necessary for management of Trillium to exercise any
      discretion in determining whether a particular service has been
      pre-approved.
|--- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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|    | In addition, pursuant to the Policy the audit committee
      has delegated its pre- approval authority to the Chair of the audit
      committee. The Chair of the audit committee is required to report any
      granted pre-approvals to the audit committee at its next scheduled
      meeting. The audit committee shall not delegate to management the audit
      committee's responsibilities for pre-approving audit and non-audit
      services to be performed by the external auditor.                                                                                                                        
|--- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|    | Pursuant to the Policy, there is an exception to the
      pre-approval requirements for permitted non-audit services, provided all
      such services were not recognized at the time of the engagement to be
      non-audit services and, once recognized, are promptly brought to the
      attention of the audit committee and approved prior to the completion of
      the audit. The aggregate amount of all services approved in this manner
      may not constitute more than five percent of the total fees paid to the
      external auditor during the fiscal year in which the services are
      provided.
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|(b) | Of the fees reported in this Annual Report on Form 40-F
      under the heading Principal Accountant Fees and Services, none of the
      fees billed by Ernst & Young LLP were approved by Trilliums audit
      committee pursuant to the de minimusexception provided by Section
      (c)(7)(i)(C) of Rule 2-01 of Regulation S- X.                                                                                                                                                                                                                                                                                   

Off-Balance Sheet Arrangements.

Trillium does not have any off-balance sheet arrangements that
have, or are reasonably likely to have, a current or future effect on its
financial condition, revenues or expenses, results of operations, liquidity,
capital expenditures or capital resources that are material to investors.

Tabular Disclosure of Contractual Obligations.

The required disclosure is included under the heading Tabular
Disclosure of Contractual Obligations in Trilliums Managements Discussion and
Analysis for the years ended December 31, 2014 and 2013, filed as Exhibit 99.2
to this Annual Report on Form 40-F.

Identification of the Audit Committee.

Trillium has a separately-designated standing audit committee
established in accordance with Section 3(a)(58)(A) of the Exchange Act. The
members of the audit committee are: Luke Beshar, Henry Friesen and Robert
Kirkman.

Mine Safety Disclosure.

Not applicable.

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Disclosure Pursuant to the Requirements of the Nasdaq
Capital Market.

As a Canadian corporation listed on the NASDAQ Capital Market,
we are not required to comply with most of the NASDAQ corporate governance
standards, so long as we comply with Canadian corporate governance practices. In
order to claim such an exemption, however, we must disclose the significant
differences between our corporate governance practices and those required to be
followed by U.S. domestic issuers under NASDAQs corporate governance standards.

Our corporate governance practices meet or exceed all
applicable Canadian requirements. They also incorporate some best practices
derived from the NASDAQ rules and comply with applicable rules adopted by the
Securities and Exchange Commission to give effect to the provisions of the
United States Sarbanes-Oxley Act of 2002.

We expect that further information about our corporate
governance practices will be included in our Information Circulars in respect of
future annual meetings of shareholders.

The following is a summary of the significant ways in which our
corporate governance practices differ from those required to be followed by U.S.
domestic issuers under NASDAQs corporate governance standards. Except as
described in this summary, we are in compliance with the NASDAQ corporate
governance standards in all significant respects.

Shareholder Approval

Section 5635 of the NASDAQ Marketplace Rules requires
shareholder approval to be obtained in connection with the undertaking of
certain actions. The circumstances under which shareholder approval is required
under the NASDAQ Marketplace Rules are not identical to the circumstances under
which shareholder approval is required under Canadian and TSX requirements. For
example, but without limitation, Section 5635 requires shareholder approval of
most equity compensation plans and material revisions to such plans. This
requirement covers plans that provide for the delivery of both newly issued and
treasury securities. The TSX rules provide that only the creation of or certain
material amendments to equity compensation plans that provide for new issuances
of securities are subject to shareholder approval. We follow the TSX rules with
respect to the requirements for shareholder approval of potential transactions,
including, without limitation, shareholder approval of equity compensation plans
and material revisions to such plans.

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UNDERTAKING AND CONSENT TO SERVICE OF PROCESS

|A. | Undertaking.
|-- | ------------

Trillium undertakes to make available, in person or by
telephone, representatives to respond to inquiries made by the Commission staff,
and to furnish promptly, when requested to do so by the Commission staff,
information relating to: the securities registered pursuant to Form 40-F; the
securities in relation to which the obligation to file an annual report on Form
40-F arises; or transactions in said securities.

|B. | Consent to Service of
Process.
|-- | ------------------------------

Trillium has concurrently filed a Form F-X in connection with
the class of securities in relation to which the obligation to file this report
arises.

Any change to the name or address of the agent for service of
process of Trillium shall be communicated promptly to the Commission by an
amendment to the Form F-X referencing the file number of Trillium.

SIGNATURES

Pursuant to the requirements of the Exchange Act, Trillium
Therapeutics Inc. certifies that it meets all of the requirements for filing on
Form 40-F and has duly caused this annual report to be signed on its behalf by
the undersigned, thereunto duly authorized, on March 24, 2015.

Trillium Therapeutics Inc.

****

By: /s/ James ParsonsName: James Parsons Title: Chief Financial
Officer

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EXHIBIT INDEX

|Exhibit | Description                                                                                                                                                                                                                            
|------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|        |                                                                                                                                                                                                                                        
|99.1    | Annual Information Form for the fiscal year ended
      December 31, 2014                                                                                                                                                              
|        |                                                                                                                                                                                                                                        
|99.2    | Managements Discussion and Analysis for the fiscal years
      ended December 31, 2014 and 2013                                                                                                                                       
|        |                                                                                                                                                                                                                                        
|99.3    | Audited Consolidated Financial Statements for the fiscal
      years ended December 31, 2014 and 2013, prepared under International Financial
      Reporting Standards as issued by the International Accounting Standards
      Board
|        |                                                                                                                                                                                                                                        
|99.4    | Certification of President & Chief Executive Officer
      pursuant to Rule 13a-14(a) or 15d-14 of the Securities Exchange Act of
      1934                                                                                           
|        |                                                                                                                                                                                                                                        
|99.5    | Certification of Chief Financial Officer pursuant to Rule
      13a-14(a) or 15d-14 of the Securities Exchange Act of 1934                                                                                                             
|        |                                                                                                                                                                                                                                        
|99.6    | Certification of Chief Executive Officer pursuant to 18
      U.S.C. Section 1350                                                                                                                                                      
|        |                                                                                                                                                                                                                                        
|99.7    | Certification of Chief Financial Officer pursuant to 18
      U.S.C. Section 1350                                                                                                                                                      
|        |                                                                                                                                                                                                                                        
|99.8    | Consent of Ernst & Young LLP                                                                                                                                                                                                           

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