Donna Moonah, 49, was last seen on Christmas Eve getting off a train on SEPTA's Market-Frankford Line at 60th and Market streets.
Police are calling her an endangered missing person.
Moonah was wearing a black jacket, blue jeans, black shoes, and a black hat the day she disappeared.
Her family is offering a $5,000 reward for her safe return.
Police are urging anyone who might know where she is to give them a call.