Mount Airy is bounded on the northwest by the Cresheim Valley, which is part of Fairmount Park. Beyond this lies Chestnut Hill. On the west side is the Wissahickon Gorge, which is also part of Fairmount Park, beyond which lies Roxborough and Manayunk. Germantown borders the southeast of Mount Airy, and Stenton Avenue marks the northeast border. Beyond Stenton Avenue is Cedarbrook and West Oak Lane.
The USPS does not officially correlate neighborhood names to Philadelphia ZIP codes (all are called simply "Philadelphia" or "Phila"). However, the 19119 ZIP code is almost entirely coterminous with the cultural-consensus boundaries of Mount Airy.