Pratt, 36, hit .272 with four homers and 20 RBI last season.
"We're pleased to have Todd back with us," said General Manager Ed Wade. "He's done a great job in a backup role."
In parts of 11 major league seasons, Pratt has a .255 career average with 35 home runs and 166 RBI in 495 games.
Teams have until midnight Sunday to offer arbitration or lose negotiating rights to players until May.
The deal likely means that catcher Kelly Stinnett will not return.
Stinnett played seven games after coming over from the Cincinnati Reds in a late-season trade, but the Phillies opted not to pick up his option.