The creative account, worth £10 million, was put up for review in August from its then agency, HHCL & Partners, which did not repitch. M&C won in a pitch between TBWA\London, Lowe Lintas and Ogilvy & Mather.
M&C will work on brand repositioning, and ehsbrann will concentrate specifically on customer relationship management.
AA marketing director Clare Salmon said: "This is the first time that the AA account has been consolidated through one pitch process, and this recognises the size and diversity of the AA advertising task in the future.
"We are pleased to have found top-quality, complementary agencies who, between them, will work with the in-house marketing team for this major repositioning strategy for the AA brand," she said.