Mejia was designated for assignment by Los Angeles on Friday.
Mejia was scooped up off waivers by the Angels on Saturday, but he'll head back to waivers following Friday night's transaction. He owns a 7.32 ERA with 21 strikeouts over 19.2 innings this season in the big leagues across stops with the Twins and Angels. Nick Tropeano was recalled from Triple-A Salt Lake in a corresponding move.