Transperth says a fault on the Mandurah rail line is not expected to be fixed until later this evening.
Services have been disrupted since early this afternoon because of a technical problem with an overhead power line near the Murdoch Station.
The cause of the problem is not yet known.
Trains have been cancelled between the Esplanade and Rockingham stations, and replacement bus services are operating.
No other lines are affected.
A Transperth spokesman says normal services are expected to be restored 9:00pm (AWST) and will run into the early hours of the morning as part of the New Years Eve timetable.
