Funds were not allocated to the project in the current budget and were transferred from the infrastructure reserve.
Commissioner Linton Reynolds said the traffic signals were required at the intersection to improve safety and optimise traffic flow.
The city has received funding from the Main Roads WA Road Improvement Program to carry out the construction works.
Civil works had been carried out but the completion of the traffic signals was delayed awaiting the approval of the railway boom gates.
Welshpool Road and Sevenoaks Street are under the care, control and management of the City of Canning but Main Roads WA would manage and maintain the traffic lights once completed.