The talented pair teamed up to perform Mendes’ hit single “In My Blood” together onstage at the 61st Annual Grammy Awards on Sunday.
Mendes started the performance solo while playing the piano before Cyrus came out to a roaring round of applause to help finish the song.
The pair is also expected to release a single together on Cyrus’ new album, due out later this year.
At the show, Mendes, 20, is nominated in two categories: song of the year for “In My Blood” and pop vocal album for his self-titled third studio album, which was released in May.
Be sure to check out PEOPLE’s full Grammys coverage to get the latest news on music’s biggest night.
On Thursday, the “Nothing Breaks Like a Heart” singer, 26, posted a black-and-white photo of her and Mendes wearing matching black leather jackets with Parton’s face printed on the back. The jacket Mendes wore featured Parton’s iconic 1978 cover of Playboy.
“This could be the year for the real thing,” Cyrus captioned the photo, quoting the lyrics to Parton’s 1983 duet with Kenny Rogers, “Islands in the Stream” ahead of the duo’s MusiCares performance.
Mendes also shared the same photo in color to his Instagram, and he captioned it with a single black heart emoji.
When Cyrus posted a photo from her Grammys rehearsal earlier in the week, fans were quick to point out that Mendes’ guitar was in the background, as well as some equipment marked with his name, and suspected that a duet from the two was on the way.
“Gram Gram rehearsals! Performing this Sunday at the @recordingacademy!” Cyrus captioned the photo she shared on Wednesday.
Additionally, Cyrus and Mendes both posted solo shots from rehearsals with credits to the same photographer, Sam Dameshek, which further increased speculation about their collaboration.
Along with Cyrus and Mendes, performers at the show also include Ricky Martin, Cardi B, Post Malone, Red Hot Chili Peppers, Janelle Monáe, Brandi Carlile, Camila Cabello, Dan + Shay, H.E.R., Chloe x Halle, Lady Gaga, Mark Ronson, Travis Scott, Dua Lipa and St. Vincent.
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The 61st Annual Grammy Awards are broadcasting live from Staples Center in Los Angeles on Sunday, Feb. 10 at 8:00 p.m. ET/5:00 p.m. PT on CBS.