The 25-year-old singer, who is a guest judge on this season's American Idol, and the frontman of Sum 41, filed for divorce in October after more than three years of marriage.
"We still work together all the time," she tells Ryan Seacrest on his KIIS radio show. "He's one of my best friends ... We've been friends for a really long time, and we always will be. We're family and we have a connection."
Lavigne says Whibley helped with the production and mixing of her new album, Pink Crust, which includes a song from Tim Burton's Alice in Wonderland, and the pair continue to "work really well together."
As for judging Idol hopefuls, Lavigne says she was wowed by the surly Simon Cowell and many of the contestants.
"I am actually really blown away by the talent of the majority of the contestants that I saw. It made it really hard to judge them," she says. "I was really impressed with Simon. … I didn't think he was mean. I thought he was really smart."