The Royals selected Waters' contract from Triple-A Omaha on Tuesday.
Waters has spent all of this season at Triple-A Omaha after being removed from the Royals' 40-man roster in late March, but he's back in the big leagues after posting a .731 OPS with 12 homers and 17 steals for Omaha. The 27-year-old will likely be utilized as an extra outfielder in Kansas City.