It was a reunion that made the hearts of "Camp Rock" fans swell all over Los Angeles. In her concert on Saturday, singer Demi Lovato was joined onstage by her ex-boyfriend and former Disney co-star Joe Jonas.

And duo performer their hit single "This is Me."

After Lovato started in on the "Camp Rock" song during her show at the Staple Center in LA, Jonas strolled out onto the stage, sending fans into a frenzy.

 Lovato and Jonas, who appeared in the first "Camp Rock" in 2008, were close friends for years and also dated briefly in 2010.

The exes appeared to be on friendly terms during the LA show on Saturday, even hugging after their duet.

"I can fortunately say that him, and his brother Nick, have always been there for me and are literally family, and like brothers," Lovato told ABC's "Nightline." "We have a great friendship."

Jonas took to social media after the concert to share his excitement over the performance with his followers.

"Surprise LA! ‪@ddlovato thank you for having me. @ Staples Center," Jonas wrote on Twitter.

The former JoBro later added, "Tonight was amazing. Fun keeping this a secret @ddlovato @ Staples Center."

Jonas also posted a clip of the pair's secret rehearsal after the show.

"Tonight was amazing. Fun keeping this a secret," wrote Jonas.

Fans erupted into applause at the sight of Jonas.

"When she started that song, we were loving it. And then when Joe Jonas came out, the crowd went crazy. They were great,"

 a source told E! News after the concert.