Emergency services were called to St Marys at 7.20pm after residents heard gunshots and phoned triple zero.
They found the man, believed to be in his early 30s, outside a home on Brisbane Street with serious bullet wounds.
He was treated by paramedics but died at the scene.
Witnesses told police they saw an unknown vehicle leaving the scene shortly after the man was shot.
A crime scene was set up and will be examined by forensic officers.
Police are yet to confirm the man’s identity.
His death is being investigated by local police and detectives from the State Crime Command’s Homicide Squad. Anyone with information should phone Crime Stoppers on 1800 333 000.