The 14-year-old victim is alleged to have been assaulted in public toilets in the Edinburgh park, on Friday, April 15.
The suspect then fled after a member of the public entered the toilets.
A spokesperson for Police Scotland said: “An 88-year-old man has been arrested in connection with an alleged sexual assault in the Meadows, Edinburgh on Friday, April 15, 2022.
“Enquiries are continuing.”