Perry, 29, will join Musgraves, 25, for the 50th episode of CMT Crossroads on June 13, but she first Tweeted her adoration of the "Merry Go 'Round" singer in 2012.
And the feeling is mutual.
"I'm just such a big fan," Musgraves recently told PEOPLE of Perry, with whom she will tour this summer. "I've never gone on tour with a strong female like [Katy], especially one that's so fun and whimsical."
Filmed at a concert in Los Angeles, the hour-long episode will feature duets of their individual hits like "Firework" and "Follow Your Arrow" as well as covers of Bonnie Raitt's "I Can't Make You Love Me" and Dolly Parton's "Here You Come Again."
Watch their performance of Perry's "Roar" below.
CMT Crossroads: Katy Perry and Kacey Musgraves premieres June 13 on CMT before encore airings on channels including VH1, MTV, MTV Hits and Palladia.