It happened around 7:30 p.m. near 10th and Locust streets.
Police tell Action News that the 25-year-old man who works for PPA was stabbed four times. The man was on-duty at the time of the incident.
The man was able to walk to an area hospital where he's currently listed in stable condition.
There is no immediate word on what sparked the attack.
Police said they have one person in custody in relation to the incident.
Anyone with any information is asked to call police at 215-686-TIPS.