It happened around 4:30 p.m. on the 800 block of South Broad Street.
Police say the 27-year-old victim was stabbed one time in her left thigh during the attack.
She was able to walk to a nearby firehouse to help.
The woman was treated and released from the hospital.
It's still unclear what sparked the attack.
No arrests have been made. Anyone with information is asked to call police at 215-686-TIPS.