Jobs Minister Stuart Ayres will become his deputy leader and Matt Kean, who is the current Environment Minister, is expected to be promoted to Treasurer.

Mr Perrottet made a brief statement after leaving the party room with his colleagues.

"I really appreciate the trust my colleagues have put in me today," he said.

While Mr Perrottet is from the less dominant right faction of the Liberal party, Mr Ayres and Mr Kean are from the moderate faction.

The party room was forced to vote for a new leader after the shock resignation of Gladys Berejiklian last Friday following an announcement that she would be investigated for alleged corruption.

Mr Stokes was largely considered an outside chance but Mr Perrottet said if he was elected he would be sure to give Mr Stokes a senior position in the ministry.

Following the vote Mr Stokes pledged his loyalty to his colleague and close friend Mr Perrottet.

"The party room had a democratic vote, I always said I would give people a choice, and they have chosen emphatically, democracy is the winner," he said.

"Dominic Perrottet will be a magnificent Premier and he has new undivided loyalty and support.

"I will use every ounce of strength in my body to make sure that he is re-elected as Premier in New South Wales when we go to the polls in 2023."

Ms Berejiklian did not attend the party room meeting today and it is understood she did not vote.

A new cabinet will be put together by Mr Perrottet after the high-profile resignations of Deputy Premier and Nationals leader John Barilaro and Transport Minister Andrew Constance over the last two days.

He will face an early test as Premier when by-elections are hold in the Mr Barilaro's electorate of Monaro, Mr Constance's seat of Bega and Ms Berejiklian's seat of Willoughby.

Mr Perrottet, 39, has had a swift rise through the ranks and was expected to win the vote today comfortably.

The father of six is a conservative Catholic and has previously said his faith shapes his politics.

He voted against the decriminalisation of abortion in 2019 and is also opposed to assisted dying.

He was appointed deputy leader and treasurer in the Berejiklian government and has been recognised for his strong economic management of NSW.

On Sunday, Mr Perrottet said if he was elected he would be extremely focused on job recovery as NSW approaches a major re-opening on October 11 for the fully vaccinated.

Mr Perrottet has not ruled out tweaking the state's roadmap out of lockdown and it has been suggested he may prefer to speed up the reopening.

Restrictions are currently scheduled to ease on October 11 after the state reaches its target of 70 per cent of residents aged over 16 being fully vaccinated.