Bradley was arrested in Los Angeles on a felony charge Tuesday morning for allegedy making a criminal threat against an unidentified woman, according to the Seattle Times.
He was released from jail on $50,000 bail.
The Mariners released a statement late Tuesday night saying they were aware of Bradley's arrest. General manager Jack Zduriencik said the team was taking the situation "very seriously" and added that the Mariners "are in the process of determining the full circumstances of what occurred today."
Bradley, a Los Angeles native, has a court appearance scheduled for Feb. 8.
The switch-hitter spent two weeks away from the Mariners in May to deal with emotional issues. He has played for eight clubs in 11 major league seasons marked by boorish behavior, suspensions and repeated run-ins with umpires and managers.
During spring training last year, Bradley called himself the Kanye West of baseball. He was acquired by the Mariners from the Cubs in a December 2009 trade and has one season remaining on the $30 million, three-year contract he signed with Chicago.
A right knee injury ended Bradley's 2010 season in late July. He batted .205 with eight homers and 29 RBIs in 73 games for Seattle before undergoing arthroscopic surgery to repair a lateral meniscus tear in August.
The Associated Press contributed to this report.