The attack took place at about 9pm on May 10, when a man answered the door of his home on Turnbull Avenue in Oakleigh East.
One of the three intruders pulled out a gun, before threatening and hitting the resident with it.
CCTV footage shows the trio pinning the resident to the ground and stealing his phone before a woman living in the same home intervened, running toward the attackers.
The three attackers fled in an unknown car, and are still on the run.
They’re described as being aged in their 20s and wearing dark clothing.
The male resident was taken to hospital with facial injuries.
Anybody with information is urged to contact Crime Stoppers on 1800 333 000.