O'Neal, 41, was stricken last week, fellow comic Jim Norton announced on the "Opie and Anthony" satellite radio talk show, where O'Neal was a frequent guest, E! News reported.
"We don't know how he is. We don't know how he's going to be," said Norton. "I didn't want to do this by myself. I wish we had more news for you."
O'Neal was recently featured on a Comedy Central roast of friend Charlie Sheen. TMZ said Sheen released a statement calling O'Neal "a gentle giant, a brilliant comedian, and a noble dude."
"Wishing him nothing but recovery, healing and laughter," Sheen said.
A statement posted on Opie and Anthony's Facebook page said the family has set up an e-mail for fans to post their well-wishes.
"Our close friend Patrice O'Neal suffered a stroke last week," the statement said. "Please respect his family and their request for privacy. An e-mail has been set up for fans to send him well-wishes and his family will make sure he gets them. You can write to LoveForPatrice@gmail.com. When we have an update on his condition, we will let you all know."