Trains on the Joondalup line are delayed as Transperth carries out emergency works on the rail infrastructure.
A Transperth spokeswoman said an issue had been spotted in the overhead powerlines, which was being fixed by maintenance staff.
Services between Leederville and Whitfords are operating every 30 minutes, while there are also minor delay on the Mandurah line.
Works are not expected to take a long period to complete.
Transperth recommends that commuters allow for extra travelling time.