EXHIBIT 99.13

CONSENT OF EXPERT

Reference is made to the Annual Report on Form 40-F (the Form
40-F) of Cameco Corporation (the Corporation) to be filed with the United States Securities and Exchange Commission pursuant to the United States Securities Exchange Act of 1934, as amended.

I hereby consent to reference to my name and my involvement in the preparation of, or supervision of the preparation of, scientific and
technical information in the following instances:



| | (a) | under the headings Operations and Projects  Uranium Operating Properties  McArthur River/Key Lake, Operations and Projects  Uranium Operating Properties  Cigar Lake,
Operations and Projects  Uranium Operating Properties  Inkai, Mineral Reserves and Resources  and Governance  Interest of Experts in the Corporations Annual Information Form for the year
ended December 31, 2016 dated March 23, 2017 for the McArthur River/Key Lake, Cigar Lake and Inkai properties; and
| | --- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| | (b) | under the headings Our Operations and Projects - Uranium Operating Properties  McArthur River mine/Key Lake mill, Our Operations and Projects  Uranium Operating Properties  Cigar
Lake, Our Operations and Projects  Uranium Operating Properties  Inkai, and Mineral Reserves and Resources in Managements Discussion and Analysis of Financial Condition and Results of Operation for the
year ended December 31, 2016 dated February 9, 2017 for the McArthur River/Key Lake, Cigar Lake and Inkai properties,
| | --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

(collectively the Technical Information) in the Form 40-F, and to the inclusion and incorporation by
reference of information derived from the Technical Information in the Form 40-F.

I also hereby
consent to the incorporation by reference of such Technical Information in the registration statements (Nos. 333-11736, 333-6180 and
333-139165) on Form S-8 for the Cameco Corporation Stock Option Plan, registration statement (No. 333-196422) on Form S-8 for the Cameco Corporation Employee Share Ownership Plan and registration statement (No. 333-200678) on Form F-10.

Sincerely,



|                       |  |                                                           
|---------------------- |  | ----------------------------------------------------------
|/s/ Alain G. Mainville
|Name:                  |  | Alain G. Mainville, P. Geo.                               
|Title:                 |  | Director, Mineral Resources Management, Cameco Corporation

Date: March 23, 2017