The bulk of the arrests came yesterday night, as authorities in riot gear confronted demonstrators.
Television news footage from outside the university's main administration building showed officers pulling people from the steps and nudging others with batons as the crowd chanted, "We are the 99 per cent!" and "Stop Beating Students!"
Thirty-two people were arrested on suspicion of resisting and delaying police officers and failing to disperse, UC Berkeley police Lt Alex Yao told the Daily Californian.
University police didn't immediately return calls from The Associated Press.
The officers eventually formed a perimeter around the steps of the building.
As the evening wore on, the crowd swelled as protesters debated whether to stay overnight.
The university reported earlier that an administrator had told the protesters they could stay around the clock for a week, but only if they didn't pitch tents or use stoves or other items that would suggest people were sleeping there.
The protesters voted not to comply with the demand and to go ahead with setting up a tent site they dubbed "Occupy Cal" to protest financial policies they blame for causing deep cuts in higher education spending.