The Bills linebacker was arrested on Friday on charges that he assaulted a woman in June, the NFL announced Friday.
According to a press release, Barnett was arrested for allegedly striking his ex-girlfriend at a hotel in Tennessee.
He is the second Bills linebacker to be arrested this year for domestic-violence offenses.
Bills defensive end Michael Johnson was arrested in April after he allegedly attacked his girlfriend in her hotel room.
The Bills have suspended linebacker Nick Bellosa for the season.