"Recorded a KILLER duet today.... Can you guess who it was with???" the singer captioned the snapshot of two people's thumbs up.
Lovato's fans quickly assumed that the person in the photo might be Nick Jonas, but the "I Really Don't Care" singer has yet to confirm or deny the rumors. Lovato recently told MTV that she and the former Jonas Brother had written "an amazing song" together, adding that she would like to collaborate with him on an album.
"I know he's working on his new album too, so it might not be for awhile, but the two of us... I'm always writing songs and he's always writing songs," she said.
2014: The Year in Music [PHOTOS]