"He sucked. He looked tired, he had trouble getting his answers out," he said. "It looks like he took my million and spent it all on weed."
Earlier this year, the comedian donated $1 million to the president's Super PAC.
Maher said his lackluster performance could also be blamed on bad timing.
"I don't know if you heard what happened this week, but his wedding anniversary was Wednesday and that was the same day as the debate. He apparently had the sex first, and was completely spent, had nothing left."
He also offered some praise for Mitt Romney.
"Romney looked like the big winner and [Obama] looked like the Big Lebowski. What the f*ck happened there?"
Maher's comments echoed remarks he made on Wednesday after the debate. He tweeted, "i can't believe i'm saying this, but Obama looks like he DOES need a teleprompter."