The 150-megawatt power station will provide electricity to state-owned utility Horizon Power and to a subsidiary of Fortescue Metals Group, a major iron ore producer in the area.
The project has been fully contracted under 25-year power purchase agreements with those two customers, and may be expanded to accommodate others in future.
TransAlta said it set out to grow its business in Australia three years ago.
"By focusing on serving large industrial customers, we've now been able to invest close to a billion dollars in Australia in assets with stable long-term contracts," said CEO Dawn Farrell in a release.
"This latest investment will have a power plant ready to serve a new customer, Horizon Power, and an existing customer, Fortescue in the Pilbara region of Western Australia by 2017."
The project's price tag includes the purchase of existing equipment from Horizon Power.
It's expected to create 250 jobs during construction and 20 once it's up and running.
TransAlta has been active in Western Australia for nearly two decades and currently has six plants in the region totalling 425 megawatts of capacity.