The joke was met with both shock and applause before a man was ejected for heckling the comedian during the Canadian show, according to reports.
While Cosby was performing his second show since a string of sexual assault allegations -- most of which involve claims that the comedian drugged his victims -- the 77-year-old seemed to improvise the sexual-assault joke, according to multiple reports.
A woman in the London, Ontario, crowd stood up, and Cosby stopped his set to ask her where she was going, the Associated Press reported. The woman replied she was going to get something to drink, at which point Cosby said, "You have to be careful about drinking around me."
According to reporters on the scene who were tweeting, the initial reaction was shock.
"'You have to be careful about drinking around me,' Cosby just said to a woman in the crowd. Loud gasps from the audience," tweeted Richard Warnica, a reporter for the National Post. "The gasps then changed to cheers and applause."
Shortly after the joke, the AP reported, an audience member yelled at Cosby that he was a rapist. The crowd began to boo the man, but Cosby told them to stop. The man was removed.
"Security just pulled a man out of the crowd in London. 'You are a rapist!' he yelled at Cosby on the way out," Warnica tweeted.
After the show, Cosby issued a statement obtained by The Times: "Dear Fans: One outburst but over 2,600 loyal, patient and courageous fans enjoyed the most wonderful medicine that exist for human-kind. Laughter. I thank you, the theatre staff (Budweiser Gardens), the event organizers and the London, ON Community for your continued honor and support. I'm Far From Finished."