Mars shared a funny video Monday on Instagram of the 27-year-old British singer serenading him at his "extra" birthday celebration.
The clip shows Sheeran singing "Happy Birthday" to "two-time Super Bowl-performing Bruno" as Mars digs into a tray of cupcakes. The video ends with Mars demanding Sheeran repeat the song.
"You know you've made it when you can hire Ed Sheeran to sing you Happy Birthday. #ExtraForever! #HappyBrunoMarsDay!" he captioned the post.
People said the clip was filmed backstage at Bridgestone Arena in Nashville, Tenn. Mars performed at the venue the same evening as part of his 24K Magic world tour.
Sheeran discussed his friendship with Mars and hinted at a future collaboration in an interview with Entertainment Tonight in August.
"I was up in the studio the other day with Bruno Mars," he shared. "We know each other very well. We hang out."
Mars released the album 24K Magic in November 2016, and will next perform Thursday in Tulsa, Okla. Sheeran is also on the road for his ÷ tour, and will take to the stage Oct. 13 in Kansas City, Mo.