The $15m (£9m) raised by Thursday night's soiree was a record amount for a single fundraiser, according to the Associated Press news agency.
Speaking about his decision to become the first sitting US president to back gay marriage, Mr Obama told guests: "The truth is, it was a logical extension of what America's supposed to be... Are we a country that includes everybody? Does that make us stronger? I believe it does."
Some 150 guests paid $40,000 a ticket to get into the event, which was held to boost Mr Obama's campaign coffers six months before he asks voters for a second term.
DreamWorks Animation chief Jeffrey Katzenberg also addressed the crowd, and recalled Mr Obama's 2008 campaign slogan, "Yes we can."
There were renewed cheers as the studio mogul added: "Yes, we have. Yesterday he did the right thing yet again."
Other guests included Barbra Streisand, Robert Downey, Jack Black, Billy Crystal, Tobey Maguire, Salma Hayek and fashion designer Diane Von Furstenberg. Clooney was joined by his girlfriend, Stacey Kiebler.
The Obama campaign also conducted an online raffle for $3 tickets, offering members of the public the chance to join the dinner.
The winners were a science teacher from Florida and utility company employee from New Jersey who is also the mother of a child with Down syndrome. Both women brought their husbands.
Mr Obama paid tribute to Clooney in remarks at the start of the evening, saying: "We raised a lot of money because everybody loves George. They like me, they love him. And rightfully so."
Republicans criticised the Tinseltown fundraiser, saying that Mr Obama was a "Celebrity in Chief" who was out of touch with ordinary Americans.
Republican National Committee Chairman Reince Priebus wrote on the Red State conservative blog: "With a first term this disastrous, we can't afford to see the second - because if we've learned anything from Hollywood, it's that the sequel is always worse."
Mr Biden's Oval Office apology to Mr Obama came on Wednesday, just before the president declared his own support for gay marriage in a hastily arranged TV interview.