The move was made Monday, before the Twins played the Boston Red Sox in an exhibition game.
The 33-year-old Boyer has pitched in parts of eight major league seasons with five teams, most recently for San Diego. Boyer had a 3.57 ERA in 32 appearances last year for the Padres, and the Twins signed him during the offseason to a minor league contract.
Boyer, who was out of baseball in 2012, has a 1.69 ERA with one walk and five strikeouts in 10 2-3 innings this spring.
He gets a $750,000 salary while in the major leagues and $100,000 while in the minors. He can earn $100,000 in performance bonuses: $25,000 each for 35, 40, 45 and 50 games as a pitcher.
Minnesota has 14 pitchers in camp and likely will trim two before the regular season.