Panik, 28, hit .235 with three home runs and 27 RBIs in 103 games this season. He's played in at least 100 games each of the last five seasons.
San Francisco also demoted pitcher Sam Selman to Triple-A Sacramento. The Giants recalled pitchers Connor Menez and Willaims Jerez from the River Cats in corresponding moves.
Panik debuted with the Giants in 2014. He had eight RBIs and played strong defense during the Giants' run to the World Series that fall.
A former first-round pick, Panik was named to the All-Star Game in 2015. He hit a career-high .312 with eight home runs and 37 RBIs before missing most of the season's final two months with a back injury.
Panik is a career .271 hitter with 36 home runs and 221 RBIs in six Major League seasons.
San Francisco is 56-57 this season. The Giants are 3 1/2 games behind the St. Louis Cardinals for the National League's second Wild Card spot.