Mars has tapped WPP's MediaCom as its global-planning agency following a review.
"This move was not a reflection of the in-market performance of our existing media-planning partners," said a Mars spokesman.
Publicis' Starcom was one of the incumbents with MediaCom.
"With the constant change in the media landscape, this model will allow us to better collaborate across our global business to drive efficiency, effectiveness, and coordination in our media planning," said a Mars spokesman. This change brings our planning model in line with our existing global creative agency structure, and will allow us to further focus media as a growth driver. We are excited about the opportunities for collaboration on the growth agenda of our brands between Mars, Mediacom, BBDO and DDB."
He confirmed that the change won't affect Starcom, which handles buying for Mars. "Starcom remains a key strategic partner in the critical area of media buying," he said.
The company, which owns M&M's, Snickers, Twix and Wrigley's, spent $692 million on U.S. measured media in 2013.
Mars earlier this year said it would seek 120-day payment terms from vendors.
Last year, parent network GroupM prevailed in a review for Nestle's U.S. media-planning and -buying duties, both traditional and digital. So the latest win puts two of the largest confectionary competitors at the network. Mars ranks No. 56 on the Ad Age DataCenter list of top advertising spenders. Nestle, which owns Kit Kat globally -- Hershey runs Kit Kat in the U.S. -- Crunch and Butterfingers, is No. 41 on the list.
MediaCom referred calls for comment to the client. "We handle competing clients in many categories through separate and protected agency structures," said a GroupM spokeswoman.
Mars in April 2014 signed a deal to buy most of Procter & Gamble Co.'s global pet-food business in a $2.9 billion cash deal.
Contributing: E.J. Schultz