The Construction, Forestry, Mining and Energy Union has begun pay negotiations with BHP Billiton on behalf of around 350 train drivers in the Pilbara.
ABC News reports the Union negotiations are the first major talks with BHP in the Pilbara for more than a decade.
CFMEU Mining district secretary Gary Wood said the Union was working hard to make sure workers were well represented in WA.
He also told ABC News the CFMEU was entering the bargaining in good faith.
"We are not going into the discussions trying to turn the world upside down, what we are trying to do is hopefully get an agreement which accommodates both the employees and the employer," he said.
The negotiations represent a continuing strengthening of CFMEU presence in the Pilbara.
Earlier this year protests by the CFMEU were held in Pilbara towns to oppose Hancock Prospecting's use of enterprise migration agreements.
Workers on Citic Pacific's Sino Iron project also walked off the job at the start of the year after meeting with the CFMEU.
Outside WA the CFMEU and BHP have been engaged in protracted and sometimes bitter negotiations over pay and conditions for Queensland coal workers.