The 24-year-old Pena, the son of former Royals manager Tony Pena, has spent the past six years in the New York Mets organization. He hit .257 last season for Triple-A Las Vegas with nine homers and 39 RBIs. He committed just three errors and threw out 30 percent of stolen-base attempts.
Pena was also a member of the champion Dominican Republic squad in this past year's World Baseball Classic, where he was 1 for 2 with an RBI in two tournament games.
The Royals announced the move on Sunday.