Mejia, a catcher/outfielder, was ranked as the No. 7 overall prospect in baseball by ESPN's Keith Law in January. He has been hot of late, batting .350 with three doubles, a triple, a home run and 10 RBIs in his past 11 games.
The Indians optioned right-hander Evan Marshall to Triple-A Columbus in a corresponding move. Marshall has a 6.75 ERA in 6 2/3 innings over nine appearances this season.
Mejia, 22, struggled in the majors when he was called up last year, hitting .154 in 14 plate appearances.
Despite his recent success in the minors, he has struggled overall in Triple-A, batting .214 with four home runs and 25 RBIs in 214 plate appearances this season. He hit .304 with 16 home runs and 61 RBIs in Double-A last season.