Several guests said attendees participated in the open 12-step process. They requested anonymity because of the nature of the meeting.
Celbrities seen coming and going from the service at the Hollywood Palladium included Lindsay Lohan, Robert Downey Jr., John Mayer and others.
DJ AM, whose real name is Adam Goldstein, was found dead last week in New York.
Police officials say pills that appeared to be the powerful painkiller OxyContin were found in his stomach and throat.
Goldstein was a recovering addict working on a reality show to help fellow addicts. He survived a plane crash in South Carolina last year.