The university said the decision to cancel the event was made at 6 p.m., two hours before the event as a crowd of more than 1,500 people gathered on the campus.
"Of paramount importance this evening was the campus's commitment to ensure the safety and security of those attending the event, the speaker, those who came to engage in lawful protest and members of the public and the Berkeley campus community," the school said in the statement.
The university condemned the violence and unlawful behavior, and regretted that "the threats and unlawful actions of a few have interfered with the exercise of First Amendment rights."
RELATED: Yiannopoulos, Shkreli event canceled after protests erupt at UC Davis
He's a self-proclaimed "internet troll" who has been widely criticized for being racist and misogynistic.
Passions started flaring around 4 p.m. between both sides on the Cal campus ahead of Yiannopoulos' 8 p.m. speech. The event is sponsored by the Berkeley College Republicans. Extra police officers were called to monitor the event.
Berkeley's student union vandalized during protest
The protests turned violent shortly before 5 p.m. as the event approached, with demonstrators lighting fires and fireworks on the Cal campus.