The incidents have happened between Sept. 21 and Oct. 24.
In each case, police say the suspect approaches the register with an item to purchase and presents cash.
Once the register is opened, the armed man demands cash from the clerk.
"He has approached the cashier in various businesses, produced a handgun and demanded money. In six of these eight incidents, he escaped with different denominations of United States currency," said Captain John Craig of Northwest Detectives.
Craig said the robberies generally occur near the Roosevelt Boulevard and include three incidents at Dollar General stores and two incidents at Dollar Tree stories.
There were also two incidents at the same Acme on Roosevelt Boulevard in Mayfair.
The first was October 17 around 8 p.m. Investigators say the robber hit a Boston Market after the Acme.
Then, on Thursday, police say they believe the same person robbed the Acme again.
Armed robber steals about $4K from ACME; suspect may be tied to other crimes: Police
There have been seven robberies and one attempted robbery in the city:
-Sept. 21, 2024, 6:25 p.m. in the 1200 block of East Erie Avenue
-Sept. 21, 2024, 6:50 p.m. in the 8400 block of Frankford Avenue
-Sept. 21, 2024, 7:13 p.m. in the 5800 block of Torresdale Avenue
-Sept. 28, 2024, 7:50 p.m. in the 400 block of Castor Avenue
-Oct. 17, 2024, 8:05 p.m. in the 6600 block of Roosevelt Boulevard
-Oct. 17, 2024, 8:20 p.m. in the 6300 block of Roosevelt Boulevard
-Oct. 24, 2024, 12:12 p.m. in the 7300 block of Oxford Avenue
-Oct. 24, 2024, 5:31 p.m. in the 6600 block of Roosevelt Boulevard
Police say the same man also robbed a Dollar General on E. Cheltenham Avenue in Cheltenham on Thursday.
Investigators say after nine incidents this robber is likely to strike again, and are warning everyone he is armed and dangerous.
"Cooperate with that individual. Your life is not worth any property," said Craig.
Police say they're also visiting stores and performing security checks, taking measures to help merchants and customers feel safe.
Anyone with information can contact Northeast Detectives at 215-686-3153 or the PPD Tip Line at 215-686-TIPS (8477). Callers can remain anonymous.