Office Depot, the product of a merger between Office Depot and OfficeMax last November, began the cross-agency review this summer.
Pile and Company supported the search.
"McCann brings proven strategic and integrated marketing expertise that will help us build a strong communications platform to deliver innovative creative work that will resonate with our customers and help us stand apart in the marketplace," said Mark Cosby, president of North America for Office Depot, in a statement.
The company added that the move comes as part of Office Depot's overall efforts to consolidate resources while expanding its advertising and marketing activities.
Fort Lauderdale-based agency Zimmerman, also part of Omnicom, was the incumbent on the Office Depot brand, handling strategy, creative, production and integrated media planning and buying.
Zimmerman could not immediately be reached for comment.
During the review, a spokeswoman said: "Office Depot has seen some dramatic change of late, and this is just business as usual. Zimmerman Advertising is proud of the work our companies have done together, and we are confident that our successful partnership will continue."
For McCann, the account adds to a string of wins, including Microsoft and Choice Hotels.
The combined Office Depot group, based in Boca Raton, Fla., spent $105 million on U.S. measured media in 2013, including OfficeMax's $34.8 million.