The party included a dinner catered by Gordon Ramsay, an auction and a performance by Scottish singer Emeli Sandé.
And, despite eager urging from many of the party's guests, John resisted calls to take the piano himself.
"This night is about Emeli. All about Emeli," he said while making his way around the final table. "You're in for a show."
The viewing party audience — which also included Quincy Jones, Carmen Electra and Bono — watched the awards on screens hanging all around the room and clapped, cheered and jeered as awards were handed out.
Bartenders in each of the tent's three outer rooms served drinks named after the best picture nominees (A Django, for instance, included vodka, coconut juice and tonic water).
In the main dining room, attendees chose between red wine-braised beef short rib and roasted red snapper.
A slight groan trickled across the room just moments into the telecast when Oscar host Seth MacFarlane joked about R&B singer Chris Brown's 2009 assault on girlfriend Rihanna. Brown, who was in attendance, didn't show any outward reaction to the joke and continued his conversation with current and former "American Idol" judges Randy Jackson and Steven Tyler.
Brown, in fact, stayed the latest of John's A-list guests — hanging out at the party well after 11 p.m. and taking time to snap pictures with a group of guests who had traveled from Slovakia.
A bright smile flashed across John's face when his friend Adele was announced the winner of the song award. While he had hoped she'd make it to the after party, it was unclear if Adele ever made it to the event.
Spotted, however, were Anna Paquin and Stephen Moyer, Heidi Klum, Miley Cyrus, Nicole Richie and Joel Madden, Britney Spears, Naomi Campbell, Lucy Lawless, Nina Dobrev, Jenna Elfman, Mena Suvari, Octavia Spencer and little Zachary Furnish-John, Elton's son with partner David Furnish.
In all, the event raised more than $6 million for the charity, with much coming from the auction.
"[The event] gets the message out that the fight against AIDS isn't over," John said. "We are still raising money for AIDS and AIDS isn't going away."
In addition to a series of paintings and photographs, attendees bid on a private five-song performance by John and a five-night stay at Steven Tyler's recently purchased vacation home in Maui.
The vacation house sparked a bidding war between Foo Fighters frontman Dave Grohl and Chelsea Handler, with both bidding more than $200,000 before another attendee jumped in and won the auction with a $230,000 bid.
John said the highlight of the event is the live musical performance, which he said separates his party from the others happening on Oscar night.
Sandé, who has toured with Coldplay, admitted to being nervous before taking the stage in front of one of the U.K.'s most beloved musicians, but John had nothing but praise for her performance.
"Last year we had Foster the People and they blew the roof off, and this year we had Emili and she blew the roof off."