Police believe the woman, who is yet to be formally identified, was first hit by a car being driven south on Ocean Beach Road at Woy Woy about 7.50pm.
The driver allegedly did not stop at the scene.
The force of the crash allegedly pushed the woman onto the road, where she was hit by a second car.
The driver of the second car, a man in his 50s, stopped to help.
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Paramedics and police tried to save the woman but she died at the scene.
The second driver was taken to Gosford Hospital for mandatory testing.
Police trying to find the driver of the first car have searched a Central Coast property and seized a vehicle, which will undergo forensic examination.
Anyone with information about the incident is urged to contact Crime Stoppers on 1800 333 000.