Exhibit 15
 
    July 30, 2010
 
    Wyndham Worldwide Corporation
    22 Sylvan Way
    Parsippany, NJ 07054
 
    We have reviewed, in accordance with the standards of the Public
    Company Accounting Oversight Board (United States), the
    unaudited interim financial information of Wyndham Worldwide
    Corporation and subsidiaries for the periods ended June 30,
    2010, and 2009, as indicated in our report dated July 30,
    2010; because we did not perform an audit, we expressed no
    opinion on that information.
 
    We are aware that our report referred to above, which is
    included in your Quarterly Report on
    Form 10-Q
    for the quarter ended June 30, 2010, is incorporated by
    reference in Registration Statement
    No. 333-136090
    on
    Form S-8
    and Registration Statement
    No. 333-155676
    on
    Form S-3.
 
    We also are aware that the aforementioned report, pursuant to
    Rule 436(c) under the Securities Act of 1933, is not
    considered a part of the Registration Statement prepared or
    certified by an accountant or a report prepared or certified by
    an accountant within the meaning of Sections 7 and 11 of
    that Act.
 
    /s/  Deloitte &
    Touche LLP
 
    Parsippany, New Jersey
 
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