Trains on the Mandurah and Joondalup Lines are experiencing delays due to a technical issue.
Trains were delayed just before 7am on Monday.
They will continue to run but will not abide by the regular schedule.
Commuters have been urged to allow extra travelling time and be aware that delayed trains may not connect with timetabled bus and train services.
If you require assistance regarding service disruptions or planning your journey, please call the Transperth InfoLine on 13 62 13.
Hearing or speech impaired people can call via NRS 133 677 and ask for 13 62 13.