Dominic Perrottet will succeed Gladys Berejiklian as New South Wales premier after winning a Liberal party room vote.
Government Whip Adam Crouch said the 39-year-old from the party's right faction beat Planning Minister and moderate Rob Stokes in the ballot at NSW Parliament on Tuesday.
It's believed there were be 39 votes for the treasurer against five for Stokes.
The devout Catholic and father of six will become the 46th person to be NSW premier and the youngest ever to take on the state's top job.
Long touted as the premier-in-waiting, Perrottet struck a deal with his moderate colleagues to make Jobs Minister Stuart Ayres his deputy and promote Environment Minister Matt Kean to treasurer.
Berejiklian quit on Friday after the state's corruption watchdog disclosed she was being investigated for potential breaches of public trust during her secret five-year relationship with former Wagga Wagga MP Daryl Maguire.
Stokes, 47, offered himself as a more experienced alternative to Perrottet, with the MP for Pittwater on Sydney's northern beaches, arguing he was the party's best shot at winning the 2023 election.
But Perrottet, who's Epping electorate is in Sydney's northwest, played up his credentials working alongside Berejiklian as deputy leader.
Australian Prime Minister Scott Morrison said he had worked with Perrottet on the NSW economy as they dealt with "the very difficult challenges we have had with Covid".
"When we disagree, we disagree. The next day we get back to work. That is how normal people get on with each other when they know each other well. And we do," he told Seven's Sunrise program on Tuesday.
Meanwhile, the NSW Nationals are preparing for their own leadership contest.
The NSW government will have an entirely fresh leadership team by Wednesday, after Deputy Premier and Nationals leader John Barilaro announced he too would quit parliament.
Paul Toole and Adam Marshall are expected to join Melinda Pavey in a three-way race to fill his position.