It happened at the Save-A-Lot store on the 4400 block of N. Broad Street in the Nicetown section around 12:40 p.m. Wednesday.
According to police, the guard repeatedly asked the man to leave the front of the store.
Chopper 6 over scene of stabbing in Tioga-Nicetown
The man refused and, after several verbal confrontations, stabbed the guard in the stomach.
The suspect then fled north on Broad Street.
The security guard was hospitalized in stable condition.
Residents say they are fed up with the violence.
"It makes no sense. The man was doing his job," said Robert Allen, of North Philadelphia.
Police say the man is known to frequent the area. He is described as a middle-aged man standing 5' 5" tall with a medium build. He was wearing a hunter green jacket, green camo pants, a gray hoodie and tan boots.
Anyone with information can call or text Philadelphia police at 215-686-TIPS (8477).
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