mejia began the 2017 season with springfield, and was promoted to memphis. on june 28, the cardinals promoted mejia to the major leagues. he made his debut the following day, against the arizona diamondbacks, when he started at second base and batted eighth, where he went 0-for-2 before being pinch hit for. he had first major league hit and home run against the washington nationals on july 1, 2017. he was outrighted to memphis on november 6, 2017.