About 30 people attended the funeral service in a chapel at Brookwood Cemetery near Woking, Surrey, The Guardian reported. They included Berezovsky's children, his attorneys and friends such as Akhmed Zakayev, a Chechen separatist leader living in London.
Berezovsky, 67, a scientist and government official in the Soviet Union, became a billionaire acquiring privatized assets in the 1990s. He was an early backer of Russian President Vladimir Putin and then one of his bitterest enemies.
"He was a friend. I miss him. I'm very grateful to Boris. Through him I felt the touch of history," a close friend, Alex Goldfarb, told The Guardian. "He was responsible for Yeltsin, and then for peace in Chechnya and then for Putin and then for anti-Putin."
The cause of death has not been definitively determined, although police have said there is no evidence of foul play. Berezovsky had been living in his ex-wife's Ascot mansion and his body was found on a bathroom floor there March 23.
Berezovsky had been forced to sell his own home to cover the cost of a long and unsuccessful legal battle with Roman Abramovich, owner of the Chelsea soccer club.
The service was delayed from Monday to foil pro-Putin Russian news agencies and to allow an Orthodox priest from Russia to perform the service, The Guardian said.