An MRI on Muncy, who is batting .253 with 33 home runs and 87 runs batted in, revealed a small fracture in the wrist, the result of him being hit by a pitch in Wednesday night's game at San Diego.
X-rays didn't reveal anything on Thursday, but a further examination Friday before the Dodgers played the Arizona Diamondbacks showed the extent of his injury.
Muncy has appeared in 129 games this season for the National League West-leading Dodgers, the second highest total on the team outside of Cody Bellinger's 131 games.
The Dodgers activated infielder Kristopher Negron from the injured list to take Muncy's place on the roster. Negron missed 10 games after going on the IL on Aug. 20 with neck stiffness.