Police were called to the Sunoco station at 1 Conshohocken State Road in Bala Cynwyd at 3:57 a.m. for the report of a robbery in progress.
Sunoco security observed the robbery via remote monitoring.
Video showed the suspect and clerk leaving the gas station's mini market.
When police arrived, there was nobody in the store.
A short time later, Philadelphia police located the clerk and returned him to the scene.
The victim was unharmed and an undisclosed amount of cash taken.
Police say it is unclear if the suspect was armed.