The incident happened at 2 a m. Monday morning inside the William Penn parking garage located at 36 South 19th Street.
Surveillance video shows the suspect sneaking past the attendant by crawling underneath the front office window.
He steals two vehicles parked inside the garage and fled in an unknown direction.
Police describe the suspect as a black male, 40-50 years-old, bald, and clean shaven with a medium build. He was wearing a black jacket, black pants and blue sneakers.
If you recognize this suspect, call Central Detectives at 215-686-3047.