Around 80 people pelted a Mandurah home with bottles and other objects, breaking all the windows and knocking holes in doors and walls.
Police are trying to track down the vandals after being called to the suburb of Silver Sands last night.
A small group of people was having a party in the Adonis Road home when gatecrashers tried to enter. A fight broke out between people in the house and the gatecrashers around 9.55pm.
The occupants of the home locked themselves inside and called police while the group of approximately 80 people pelted the home with bottles, smashing windows.
Police said extensive damage was done to the home with all windows being broken and holes knocked into doors and walls.
"The majority of people dispersed on hearing police attending and inquiries are continuing into the identity of those involved in the damage to the home," a police spokeswoman said.