Pena, 35, likely will provide organizational depth at Triple-A Omaha. Last year's catcher at the affiliate, Tony Cruz, was designated for assignment earlier this offseason and subsequently released.
Pena played four seasons for the Royals from 2009-12, with his best season coming in '09, when he hit .273 with six homers and 18 RBIs.
Pena was one of the more popular players in the Royals' clubhouse during that stretch.
Pena is a .259/.299/.351 career hitter in 12 Major League seasons.
Pena was a regular with the Reds in 2014 and '15, and he played nine games for the Cardinals last season.
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.