Cox has already made a guest appearance on Perry's now-cancelled NBC comedy 'Go On' and he is returning the favour by making an appearance on her TBS comedy, reported Us magazine.
The 'Friends' stars have been reuniting off and on. Perry and Lisa Kudrow appeared on an episode of Jane Lynch's summer comedy game show 'Celebrity Game Night' while Jennifer Aniston and Kurdrow also guest starred on 'Cougar Town' in 2010.
Perry, 49, and Cox, 44, starred on Friends from 1994 to 2004. They played on-screen spouses Monica Gellar and Chandler Bing on the 10-season hit sitcom.