The latest victim, an 18-year-old man, was sitting in a parked car on Tench Avenue in Jamisontown, near Penrith, when shots were fired at the vehicle late last night.
He took himself to Nepean Hospital after he suffered gunshot wounds to his legs. Police were called to the hospital at 11.30pm.
The man was treated for the injuries to his leg, which are understood to be non-life-threatening.
It comes just three days after a man in his 20s was shot while he was parked on Hickeys Lane in Penrith.
He also suffered non-life-threatening injuries.
Police have not linked the two shootings.
Anyone with any information about the shooting should contact Crime Stoppers.
