The robbery happened around 3:00 p.m. in the 100 block of City Avenue.
Police say the suspect entered a 7-11 armed with a handgun.
He pointed the gun at a store clerk and demanded money from the drawer.
He fled the store with the cash, running westbound on Oakland Terrace.
There were no reports of injuries.
The suspect is described as a black male in his 20's and 5'10" tall.
He was wearing a dark colored hooded pullover and white converse sneakers (Chuck Taylor style).
Police say a similar robbery happened back on August 28th and they are investigating to see if there is a connection.
Anyone with information is asked to call the Lower Merion Police at 610-649-1000.