He has previously played in Nippon Professional Baseball (NPB) for the Hiroshima Toyo Carp.

On May 28, 2011, Mejía signed with the St. Louis Cardinals organization as an international free agent.

On March 18, 2022, Mejía signed with the Pericos de Puebla of the Mexican League.

[5] On May 13, 2023, Mejía signed with the Bravos de León of the Mexican League.

On June 14, 2024, Mejía and Keven Lamas were traded to the Saraperos de Saltillo of the Mexican League in exchange for Henry Urrutia and Rainel Rosario.