Deb Frecklington will lead the LNP in Queensland following the party's defeat at the November 25 election.
Emerging from a party room meeting on Tuesday afternoon, opposition whip Trevor Watts announced Ms Frecklington won the vote against contender John-Paul Langbroek.
The party was yet to reveal by how many votes Ms Frecklington and Mr Mander won.
Former leader Tim Nicholls announced he would not recontest the leadership, after it was confirmed Labor won majority government with 48 seats, while the LNP had 39.
Member for Oodgeroo Mark Robinson, who called himself the "underdog", also unsuccessfully challenged for leader, while Jason Costigan lost the vote to be deputy leader.
Ms Frecklington walked into the meeting flanked by 11 MPs, including deputy hopeful Mr Mander, Mr Nicholls, Ros Bates, and Andrew Powell, while Mr Langbroek entered the room with just one, Mark McArdle.
Speaking to reporters, Ms Frecklington said the new leadership team had pressed the "reset button" with a "revitalised new party".
"We are under no illusions of the hard work that we will have to do to rebuild the faith of Queenslanders," she said.
"With me, what you see is what you get, I will be a no frills politician.
"And in saying that, I have one thing to say to Annastacia Palaszczuk and Labor - it is game on."
Ms Frecklington said she would have discussions with Mr Mander and her colleagues about the shadow frontbench "over the next couple of days", but did not elaborate on whether Mr Nicholls would get a role.
She said the "people of Queensland" had spoken.
"We've just lost an election, we know we've made some mistakes, and that is what both Tim Mander and myself and the whole LNP team will be getting together in the coming days, we'll be discussing many things over the coming months," she said.
But Ms Frecklington did not explain what mistakes were made during the election campaign.
"We're standing here today, we lost the election, we made some mistakes in that election, like, well, we need to get around to Queensland and rebuild the faith, we need to be talking to those disaffected voters, we need to be understanding what it is that they want to hear from us," she said.
Ms Frecklington will be the first woman to lead the merged LNP and it will be the first time Queensland had a female leader of both major parties.
LNP president Gary Spence congratulated Ms Frecklington on becoming the new LNP leader and also becoming the party's first female parliamentary leader.
"Deb has had a meteoric rise since first entering Parliament in 2012 after winning the seat of Nanango," he said.
Mr Spence also congratulated Mr Mander, and said they both brought experience into the roles.
"I am excited about the prospects of our new parliamentary team led by Deb Frecklington and Tim Mander, and I look forward to them building a strong, positive opposition that holds the Palaszczuk government to account," he said.
Earlier in the day, Labor's new cabinet was sworn in at Government House.
Meanwhile, Steve Dickson, who lost his seat of Buderim, confirmed he would remain the Queensland leader of One Nation from outside the Parliament.
His duties will include supporting the party's solitary MP, member for Mirani Stephen Andrew, and preparing for the next Queensland election.
