Josh Brolin is trying to live up to his promise ... he's reportedly checked into rehab after telling TMZ he was swearing off booze for good.
Brolin checked into a rehab facility recently in Northern California ... a source told Us Weekly he realized he needed help and is committed to his sobriety.
TMZ broke the stories ... Josh got into into a drunken barfight in Santa Monica earlier this month that was caught on video ... and that same weekend, he tangled with a cab driver after rear-ending the guy.
A few days later, he swore to us he was changing his ways ... saying he'd never touch a drop of alcohol again.
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