The accident occurred shortly after 2:00 a.m. Wednesday at Cedar and East Cumberland streets in Philadelphia's Kensington section.
The officer, identified by police sources as 28-year-old Mike Brady, was crossing the intersection when he was struck by a vehicle, police say.
Police say the driver stopped about a half-block after the impact, but not to aid the stricken pedestrian.
"A female passenger gets out, examines the car, gets back into the car and the car continues east toward York Street and Aramingo Avenue and left the scene, left him there," said Capt. John Wilcynski of the Philadelphia Police.
Police arrived to find Brady leaning against a car and bleeding.
Police released surveillance video of the incident, which shows the car speeding down the street before coming to an abrupt stop.
Officer Brady was taken to Hahnemann University Hospital and treated for a gash to his head and is now listed in stable condition.
Action News has learned that Brady, a five-year veteran of the force who works in the 3rd District, was walking to his grandmother's house when he was hit.
The vehicle involved is believed to be black or dark-colored 2010 Ford Taurus. Police say the car may have minor damage to the passenger side, is missing a windshield wiper arm and may also have a dented hood.
The car was last seen heading east on Cumberland Street toward Aramingo Avenue.
Anyone with information is asked to contact Philadelphia Police at 215.686.TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.