Thieves stripped 268m of contact wire overnight on the train line between Kuils River and Bellville, Metrorail said on Monday.
The overhead wire was taken from a site near the R300 bridge, spokesperson Riana Scott said.
"Technical teams finishing off their repairs and the line should reopen in time for afternoon peak, if not earlier," she said.
As a result of the theft, inbound Muldersvlei trains had to be rerouted via Kraaifontein and trains were temporarily suspended between Strand and Bellville.
Last month, it was announced that the deployment of the Rail Enforcement Unit would be extended for another year.
The provincial transport and public works department, the Passenger Rail Service of South Africa (Prasa) and the City of Cape Town said in a joint statement that they were committed to keeping commuters and infrastructure safe.
The unit of 100 officers has assisted Prasa's regional protection services unit since its inception in October last year.
Rewards of up to R25 000 are payable for information leading to successful convictions for railway-related crime.
Members of the public can call the Metrorail Protection Services hotline on 021 449 4336/5056, Crime Stop on 0860 10111 or send an SMS to the crime line on 32211.