If elected, she would be the first woman member of Monaro in its 165-year history.

As flagged by Australian Community Media this week, Ms Overall has for some time been courted to make a tilt for NSW Parliament and the revelation of her husband Tim's retirement as the long-running mayor of Queanbeyan-Palerang was thought to be confirmation an announcement on her political future was imminent.

"I can't deny it's been a whirlwind week," she said.

Ms Overall on Saturday confirmed her candidacy in Queanbeyan, the as-yet unscheduled byelection for the southern NSW seat of Monaro necessary after Mr Barilaro earlier this month announced he was leaving State Parliament.

Ms Overall said she had been considering standing for State Parliament in 2023 but the resignation of Mr Barilaro had brought that intention forward and she had decided to "seize the day".

"I'm honoured to be preselected today for the Nationals," she said.

"I truly believe the Nationals are the party that are the closest to the people. They are grassroots. They are about the community. It's what I have always been about myself."

Ms Overall stood for preselection unopposed but her candidacy still went to the vote of the Nationals' grassroots members, which was held virtually on Saturday, due to the restrictions of COVID.

Mr Barilaro welcomed Ms Overall's preselection by saying she was a strong advocate for the region.

"I have known Nichole for many years and over that time I have been left in awe with how dedicated she is to our community," Mr Barilaro said.

"From her work with the Meals on Wheels Queanbeyan Branch, Headspace Queanbeyan and the Red Cross - Nichole's passion for helping others is unrivalled.

"In 2020, Nichole was named Monaro Woman of the Year for this very reason. She is always the first person to put her hand up if you need a hand.

"The decision to retire as the Member for Monaro was not an easy one, but I know Nichole is the best candidate for the job - she will take up the fight for the region to ensure the Monaro gets its fair share."

Saturday's announcement was made alongside Deputy Premier Paul Toole and Minister for Women Bronnie Taylor in Queanbeyan, the heart of the electorate, which spans from Captains Flat and Braidwood, to the Snowy Mountains.

Mr Toole said Ms Overall would be an energetic and passionate member, saying she was "a straight-shooter".

"She's someone who has been very strong in the community for a number of decades," he said.

"... I couldn't ask for a better candidate."

Ms Overall said her focus would be on helping the region emerge from the COVID pandemic and its continuing recovery from the devastating 2019-2020 bushfires.

The commitment to the job of state member was not lost on her, after seeing her husband in local government for 17 years.

"Our sons, now 24 and 22, have virtually known little else but their dad being a local representative. So, yes, that was definitely a consideration," she said.

"But I think the other thing that helped make up my mind is that I'm going into this wide-eyed. I'm not naive, I'm not aware of the difficulties, the challenges, the workload."

While it has existed since 1856, Monaro, in its latest incarnation, since 1927, has swung between Labor and conservative parties.

Ms Overall said John Barilaro had set up the seat for a conservative win, going from scraping in in 2011, to creating an almost 12 per cent margin for the Nationals.

"So that is an extraordinary testament to the work he has done, that the National Party has invested in this seat and the support that is continuing to emerge for me to hopefully continue that legacy," she said.

The by-election date is yet to be announced.