Bad blood between the two dates back to NBC sacking O'Brien as host of its flagship late night programme The Tonight Show in favour of reinstating Jay Leno in 2010.
O'Brien admitted in a new interview with The Hollywood Reporter that he is still not on good terms with Leno after he agreed to return to The Tonight Show.
"The odds are we will both leave this Earth without speaking to each other, which is fine," O'Brien said. "There's really nothing to say. We both know the deal. He knows; I know. I'd rather just forget."
O'Brien went on to say that the only solace in losing The Tonight Show is that NBCUniversal CEO Jeff Zucker and other executives responsible for his exit were also later let go.
"It helps that almost everybody involved in the craziness has been relieved of their jobs," the comic quipped.
O'Brien previously described his Tonight Show dismissal as "a very human situation" that people could relate to.
He currently hosts Conan, which airs Mondays through Thursdays at 11/10c on TBS.
Watch a clip from Conan O'Brien's last Tonight Show below: