It happened on the 800 block of East Allegheny Avenue in Kensington just before 2 a.m., the department said.
Investigators believe the carjacker stole the silver 2012 Buick Verona and fled north on the 3200 block of G Street. The woman was found safe by 11 a.m., but the suspect is still sought, police said.
He is described as thin with a light complexion and was wearing a mask, a black puffer coat with the hood up, and black pants, according to detectives.
The Buick has Delaware tags numbered 323204.
Anyone with information should call PPD's Special Victims Unit at 215-685-3251.
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