The fire started in Bold Park and early on Monday it was controlled but not contained, as firefighters worked to strengthen containment lines.
Local resident Caroline Crundall said there was a strong breeze but little smoke to be seen from the southern end of large area of bushland.
"It's not a good day for a bushfire," she told AAP.
A watch and act alert is in place for an area bounded by Oceanic Drive, Perry Lakes Drive, Stephenson Avenue, Rochdale Road and West Coast Highway in parts of City Beach, Floreat and Mount Claremont in the cities of Cambridge and Nedlands.
"There is a possible threat to lives and homes as a fire is burning in the area and the conditions are changing," the alert from the Department of Fire and Emergency Services said.
It urged residents to leave the area if the way was clear or to make final preparations if they planned to defend their homes.
Federal Emergency Management Minister Murray Watt told ABC TV he was being briefed on the Perth fire.
"It does seem to be manageable at this point in time but it certainly something to watch. When the fire gets to a watch and act level, that's obviously something of concern."Â
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