The Poker Face star completed work on Hello, Hello earlier this week, which will feature in upcoming animated Disney flick, Gnomeo And Juliet.
Gaga posted the snap on her Twitter page, alongside a message announcing the recording was nearing completion.
She wrote: 'Eltoneo + Guliet [sic]! Finishing our duet Hello, Hello in studio. Sounding so amazing, some last finishing touches and off to the movies!'
The collaboration between the two artists, who performed together at February's Grammy Awards, will be released as part of the movie's original soundtrack.
Sir Elton has previously said that he wanted to work with the New York-born singer, real name Stefani Germanotta, and was rumoured to be working on a track for her new album, Born This Way.
'I'd love to [work with her] in the future,' he recently told Entertainment Weekly.
'There's a chance I might do one track with her [for Born This Way], but it's just, she's so busy, and I'm so busy, we can never get together!'
Gnomeo And Juliet will feature the voices of James McAvoy and Emily Blunt as the title characters. Michael Caine, Stephen Merchant and Ozzy Osbourne are also said to have been working on the project, which is due for release in February 2011.
Hello, Hello is Gaga's first contribution to a film.