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, 2014 dated March 6, 2015 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/Key Lake, 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, 2014 dated February 9, 2015 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 statements (Nos.333-181577 and 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 6, 2015