The Twins announced the moves before Saturday's game against the Kansas City Royals at Target Field. Buxton hit the injured list with a left shoulder subluxation, while Pineda landed on the IL due to a right triceps strain.
"Obviously a tough day for [Buxton] and for us, but that said, he's going to work through the rehab part of this process, and hopefully in a few weeks we have some good positive updates and we can get him back out there," Twins manager Rocco Baldelli told reporters.
Buxton previously missed 13 games this season due to a bruised right wrist. He also missed 10 contests because of concussion-like symptoms. It marks his third trip to the injured list in 2019.
Buxton, who suffered his shoulder injury after colliding with the wall Thursday against the Miami Marlins, has a .262 batting average with 10 home runs, 46 RBIs and 14 stolen bases in 2019. He also ranks as one of the top defensive outfielders in MLB.
Pineda has a 7-5 record and 4.15 ERA in 21 starts this season.
The Twins reinstated first baseman C.J. Cron from the 10-day injured list Saturday. Minnesota also recalled right-hander Zack Littell and outfielder Jake Cave from Triple-A Rochester.