Police are searching for an arsonist who set fire to the head office of a not-for-profit organisation in Guildford overnight.
About 2.40am, firefighters responded to reports of a blaze at People Who Care on James Street.
Flames had spread to the roof of the building after furniture out the front was set alight.
Crews from Bassendean, Belmont and Midland worked quickly to extinguish the fire, but could not stop it causing $20,000 damage.
People Who Care is a Perth-based volunteer organisation which serves the frail aged and disabled.
The charity helps people with special needs maintain their independence.