Ms Beazley, the daughter of WA Governor and former federal Labor leader Kim Beazley, will contest the safe Labor seat of Victoria Park at the March state election.

Mr Wyatt, 46, announced in February that he would not continue beyond the state election next March, citing family health reasons.

Weeks later, he reversed the decision and said he wanted to stay to help the state through the coronavirus crisis and beyond.

But in a statement on Monday, Mr Wyatt - a father of two daughters whose wife has battled breast cancer - announced he had again changed his mind.

Ms Beazley had been selected to run for the seat when Mr Wyatt initially announced his retirement.

She has made three previous unsuccessful tilts at office, including a run for the marginal Perth electorate of Swan at last year's federal election.

"Hannah is a fantastic local candidate with a strong record of achievement throughout her career," Premier Mark McGowan said in a statement on Wednesday.

"There's no doubt that replacing Ben Wyatt is a huge task, but I can assure the people of Victoria Park that no one is better placed to do so than Hannah."

Ms Beazley, a mother of two and director at Labor-aligned lobbyist Hawker Britton, said she was proud to be the candidate for Victoria Park.

"I won't be taking anything for granted and look forward to getting out into the community as much as possible in the coming months," she said.

The premier has refused to be drawn on who might replace Mr Wyatt as treasurer.

Transport Minister Rita Saffioti and deputy premier Roger Cook loom as possible contenders with Labor widely expected to win a second term in government.

Australian Associated Press