Most of the protesters left quietly, but one group used scrap lumber to create a circular barricade, The Guardian reported. It was eventually dismantled.
The eviction followed a High Court ruling in favor of the City of London Corp. The court refused to grant a stay to allow protesters to appeal to the European Court of Human Rights.
The bailiffs swept in after midnight to enforce the court order to clear out the plaza, dismantling platforms and tossing tents into garbage trucks.
Some of the campers said they planned to move to a protest site in London's Finsbury Square, The Daily Telegraph reported.
Occupy London began last fall as Occupy the London Stock Exchange. Because the stock exchange is situated in a development that is private property, protesters set up camp outside St. Paul's.
Catherine Brogan, a poet and member of the Occupy movement, told The Guardian many of those in the square were caught by surprise.
"This has always been a peaceful process, and it has never looked like turning into anything other than that," she added. "There's definitely no Molotov cocktails stashed, it is very timid. I just hope the police respect that, and don't react in the way I've seen them reacting at other times, at other protests."
St. Paul's Cathedral said it regretted the dismantling of the encampment.
"In the past few months, we have all been made to re-examine important issues about social and economic justice and the role the cathedral can play," a spokesman said. "We regret the camp had to be removed by bailiffs but we are fully committed to continuing to promote these issues through our worship, teaching and Institute."