Residents in the semi-rural suburb of Martin, near Gosnells and the Korung National Park, are being warned to act immediately as a fire approaches a residential area.
Firefighters are battling the blaze which is uncontained and moving in a northwesterly direction.
Affected residents should leave now if the path is clear or prepare to shelter in their homes, the Department of Fire and Emergency Services said on Tuesday.
An emergency warning has also been issued for people on rural properties west of Mullalyup State Forest near Kirup, about 220km south of Perth.
"You are in danger and need to act immediately to survive. There is a threat to lives and homes," the department said.
"The alert level for this fire has been upgraded as the situation has escalated and the fire is moving towards farms and homes."