Patridge, who came seventh in the 2010 series of the show, revealed that she spoke with Cavallari recently to tell her what to expect.
"I actually talked to [Kristin] last week," Patridge told People. "She texted me and she was like, 'Hey, I was just thinking of you and I wanted to tell you I'm doing Dancing with the Stars'.
"I was like, 'Yeah, you're going to have an amazing time. You'll be in the best shape of your life!'" Patridge continued. "I told her it's going to get hard, but just have fun with it. I had a blast."
The Audrina star explained that during her time on the show she "lived" ballroom dancing for almost four months.
"I think she'll do well," Patridge added, regarding Cavallari's chances of walking away as the champion.
Dancing with the Stars returns to ABC with a two-hour premiere on September 19 at 8/7c.
> Dancing with the Stars: Meet the new cast