Kimmel's bad blood with the presenter dates back to the 2010 Tonight Show controversy, where Leno returned to the series after Conan O'Brien was sacked.
The Jimmy Kimmel Live host openly mocked Leno by dressing as him on the air and later criticised both NBC and his late-night rival in a Jay Leno Show interview.
Kimmel revisited the feud while speaking to Deadline, revealing that he doesn't respect the Tonight Show comic.
"I mean, Jay's a very polite guy. He's a very, well, he's polite. But it's funny, people ask me about him a lot, so he must be important in some way. I'm just not a big fan," Kimmel declared.
He shared kinder words for David Letterman, who he acknowledged as his greatest comic influence.
"I know it's probably disturbing to say you idolise somebody, but if I had to pick somebody to say that about, it would probably be him," Kimmel said of Letterman.
Jimmy Kimmel Live airs weeknights at 12/11c on ABC.
Watch Jimmy Kimmel impersonate Jay Leno below: