The pair have a long-running feud dating back to the 2010 Tonight Show controversy, when Leno returned to the show and replaced Conan O'Brien.
In a new interview with Rolling Stone, obtained by the New York Daily News, Kimmel has continued his disagreement with Leno.
"As a comedian, you can't not have disdain for what he's done," Kimmel said. "He totally sold out. He was a master chef who opened a Burger King."
The comments come just before Jimmy Kimmel Live! moves to 11.35pm from next week, placing it in direct competition with The Tonight Show with Jay Leno.
Kimmel has previously explained his feud with Leno, suggesting that the comedian has acted "inappropriately".
However, Kimmel praised his other competition in the Rolling Stone interview, saying: "If I beat David Letterman in the ratings, does that mean I'm better than Letterman? No f**king way."
He also admitted that he is not concerned about a rivalry with Jimmy Fallon, saying: "People are going to compare me and him for years to come - we're being positioned as the Leno and Letterman of the next round. I like it because he's a very worthy competitor."
Jimmy Kimmel Live! was recently nominated for a Producers Guild of America award.