McCartney, 74, will make a guest appearance on Starr's latest record, a follow-up to his 2015 album 'Postcards from Paradise', reported The Guardian.
Starr, 76, took to Twitter to share the pictures and thank his former bandmate for joining him in the studio.
"Thanks for coming over man and playing great bass. I love you man - peace and love," he captioned the picture.
Also joining the former Beatles in the studio was Eagles guitarist Joe Walsh, who Starr said had "come out to play".
McCartney and Starr's last collaboration was on the tracks "Peace Dream" and "Walk With You" on the drummer's album 'Y Not' in 2010.