The 32-year-old Bradley had been put on a restricted list on May 6 after he lashed out at manager Don Wakamatsu for benching him during a game.
Bradley, who has a history of angry outbursts, then approached the organization for help in dealing with his emotions, although the Mariners would not go into details about what specific treatment he received.
"I needed help, you know, to allow me to get better, focus back on the game that I love and enjoy playing," Bradley told reporters prior to the Mariners' 3-2 loss to the Toronto Blue Jays.
"I am not saying I'm cured or whatever you call it, but I am working ever so hard and I am committed to this process."
Bradley was ordered to receive anger management while playing for the Los Angeles Dodgers in 2004 when he was suspended for five games for slamming a water bottle in the direction of a fan.
Now playing for his eighth team in the last 10 seasons, Bradley went 2-for-4 on his return but is batting just .230 with two home runs this campaign.
(Reporting by Jahmal Corner in Los Angeles; Editing by John O'Brien)