DALLAS — GSD&M has won the estimated $25 million advertising account of the AARP, the client said.

Omnicom’s Austin, Texas-based agency bested Mullen, the Interpublic Group shop in Wenham, Mass., for the creative and media account of the association. Incumbent GMMB of Washington, D.C., did not participate.

BBDO in New York, The Richards Group of Dallas and McKinney & Silver in Raleigh, N.C., had been among the initial contenders, sources said.

GSD&M and Mullen made final pitches yesterday at the Washington headquarters of the nonprofit organization, which was formerly known as the American Association of Retired Persons.

The AARP asked finalists to position it as a resource that current and prospective members can use before and after retirement, sources said. The organization works as an advocate on legislative, consumer and legal issues and offers additional benefits to its 35 million members. It recently launched My Generation, a magazine aimed at baby boomers.