Guards have walked off the job at a WA prison, striking over staffing and safety concerns.

About 50 guards undertook a three-hour industrial action at Eastern Goldfields Regional Prison (EGRP).

It comes just months after a mass riot and breakout at Greenough Regional Prison near Geraldton, which was found to have been caused by staff shortages and frequent cell lockdowns.

The WA Prison Officers' Union says the Kalgoorlie facility has about 150 prison officers, but 26 vacancies.

Union secretary Andy Smith said the prison relies on guards working overtime to stay operational.

“In order to man the prison to the safe staffing levels, our members are working inordinate numbers of overtime, so they work fatigued,” he said.

“If we don't fill those positions, we have the potential of another Greenough situation, where we don't have prison officers on duty, keeping the prison safe.”

Over 90 officers are on a waitlist to be transferred back to Perth, after serving their required regional time.

The union wants stronger incentives to encourage staff to move to Kalgoorlie, such as housing and utilities assistance.

EGRP Superintendent John Hedges says 45 graduate prison officers will start by June, which should help alleviate the staff shortage.

The union has not ruled out further industrial action.