A woman has been carjacked at knifepoint in Melbourne's north-west in a terrifying ordeal.

Police say a man with his face covered by a scarf approached the woman as she sat in her car on Raleigh Street, near Pascoe Vale Road in Essendon, about 10.30pm on Saturday, April 5.

The man ordered her to get out of the silver 2005 Volkswagen Golf and pulled his shirt aside to reveal a large knife, police say.

The victim complied and the man drove off with the car, turning left onto Pascoe Vale Road.