NSW Labor state secretary Bob Nanva will move to the state upper house after a call-up by Opposition Leader Chris Minns.
The winnable, seventh position on Labor's ballot was opened last Friday when embattled Canterbury-Bankstown mayor Khal Asfour withdrew over an expenses scandal.
Mr Minns said it was important Labor moved quickly to fill the vacancy.
"I do not believe a protracted preselection is in the best interests of NSW Labor right now, and I believe Bob Nanva will be a first class candidate for the NSW Legislative Council," he said in a statement.
"As a result I asked Bob Nanva to agree to be nominated for the vacancy on the Labor upper house ticket."
Mr Nanva led the overhaul of the party after a donation scandal was exposed.
He previously served as national secretary of the Rail, Tram and Bus Union and has been a policy adviser to Labor governments.
Mr Nanva reportedly tried to secure a spot on the upper house ticket in September but was rebuffed by Mr Minns.
"As NSW Labor General Secretary, Bob has always been a strong advocate for his Western Sydney community where he lives with his four children, and if elected I have no doubt he will continue to champion the interests of Western Sydney in his new parliamentary role," Mr Minns said on Wednesday.
Mr Asfour stepped aside when a media report on his mayoral expenses followed months of attacks over alleged links to the Obeids, which he denied.
"The latest headlines are the last straw," his spokesperson said on Friday.
"The mayor is vehemently denying any wrongdoing and has at all times adhered to the policy set by council, a policy scrutinised by the office of local government."
NSW polls open on March 18, a week ahead of election day.