Behar, who quit the program this past August after 16 years, said on Wednesday's edition of "The Tonight Show with Jay Leno" that Barbara Walters told her in 2006 she wasn't going to renew her contract because Behar confirmed O'Donnell's casting during an interview with "Entertainment Tonight."
"You ever feel like you're going to have a heart attack?" E! News said Behar asked Leno.
Behar went on to say Walters called her and said: "Hello, Joy? It's Barbara. And I just want you to know I'm not renewing your contract."
Behar said she repeatedly apologized and swore, "It was a mistake," to which Walters reportedly replied: "It was a big mistake! I'm not renewing your contract!"
Behar did not explain why Walters ultimately had a change of heart and renewed her contract, E! News said.