The French auction house Drouot maintains that the statue, of a masked figure carrying a shield, is genuine and more than 1,000 years old.
But Mexico’s National Institute of Anthropology and History says it does not match the style of the period it was supposedly from.
Another 66 pieces at Monday’s auction were also fakes, the institute said.
The Mexican foreign ministry has informed French authorities.
Story: BBC News | Photo: Binoche & Giquello/Pierre Yves Dhinaut