Los Angeles Sheriff's deputy Tony Moore said Brown was released at 12:01 a.m. Monday.
Brown had been in custody since mid-March, when he was arrested after being expelled from a court-ordered rehab sentence for violating its rules.
In his May 9 decision, Superior Court Judge James R. Brandlin sentenced the singer to serve an additional 131 days in jail, but he had been expected to get out much sooner.
Brandlin had sentenced Brown to serve a year in county jail but gave him credit for nearly eight months.
The credits include time that the singer has spent in rehab and jail, as well as credits for good behavior while behind bars.