Brown did not play in the weekend's matches against Richmond and Carlton and injured the knee at training at Gosch's Paddock on Monday morning.
He immediately underwent MRI scans where it was revealed that he had ruptured the ligament.
Brown was a key part of Collingwood's premiership campaign last year. He was a late inclusion for Simon Prestigiacomo in the first drawn grand final and played an important role in blanketing St Kilda captain Nick Riewoldt in the replay.
Brown's twin brother, West Coast's Mitchell Brown, missed a season of football when he ruptured his anterior cruciate ligament in the 2008 pre-season.
The Collingwood premiership player has played 50 games since making his debut in 2008.
