In August, Williams, 55, announced that he was seeking treatment for alcoholism. He said he had been sober for 20 years when he started drinking again.
"I'm doing great," said Williams at the movie premiere. "I want to thank the millions and the thousands and also the people that have come up in person and thank them for all their support. It's been loving. It's been wonderful to know I'm not alone. That's the main thing, when you come out of rehab. If you know that, then you've got a great shot."
In "Man of the Year," Williams reunites with director Barry Levinson ("Good Morning, Vietnam"), playing the role of Todd Dobbs, the nation's funniest man, who becomes president of the United States.
This election season, comic actors such as Lewis Black feels this is a film from which politicians can benefit.
"Certain comedy can come from … honesty," explained Black. "It would be nice if politicians might learn that. It's a muscle that's got to be developed, and 60 to 70 percent of the guys who work in Congress never developed a muscle. Have no idea the muscle exists, take themselves way too seriously and actually think they are in. And it's disgusting."
"Man of the Year" opens in U.S. theaters on Oct. 13.