The Beatles legend recently headed to the U.S. to restart his postponed tour after a bout of ill health which landed him in hospital in Japan.
It has now emerged MCCartney has been taking part in secret studio sessions with a trio of famous stars inbetween his tour dates.
Perry reveals the group recorded together but he refuses to give any more detail about the top secret project, telling the Chicago Sun-Times newspaper, "It's the great ego leveler. I was in the studio with Alice Cooper and Johnny Depp, playing guitar, and the three of us are looking at each other like, hey, we're sitting here with Paul MCCartney! And we're all looking at each other like open-mouthed kids.
"Paul was really nice. He's all about business (when he's recording). At 72 he can still hit all those notes... It's a project that we're keeping under wraps for now. There will be (an announcement when the time is right)."
He adds of working with MCCartney, "I met him once or twice (over the years) to say hello. To spend six or eight hours in (a) studio with him recording! He makes you feel like (you're recording with just another guy). He just happens to be a motherf**king huge talent!"
The news comes just days after Hollywood actor Depp joined Perry's band Aerosmith on stage at their gig in Massachusetts to play guitar.