Labor's Steve Whan and Nationals' Nichole Overall face off in NSW seat of Monaro

The Nationals' Nichole Overall had held the seat with a margin of 11.6 per cent, after winning it at a by-election a year ago.

After counting paused on Saturday night, figures showed Mr Whan had achieved a swing to Labor of 15.46 per cent on first preference votes.

The ABC called the seat for Labor by 7.45pm. No votes will be counted on Sunday.

Both the Nationals and Labor candidates had liked their chances of taking the seat in the final hours of campaigning before polls closed on Saturday.

Voting closed at 6pm, and counting continued until 10.30pm on Saturday to determine the outcome in what is considered a safe Nationals seat but has been a frequent barometer of the statewide electoral mood.

Labor's candidate Steve Whan cast his ballots for the election at Queanbeyan South Primary School, vying to regain the seat he formerly held between 2003 and 2011.

Mr Whan said it was hard to know how the election would turn, but the response to his campaign had been generally positive.

"I've had overwhelmingly positive comments from people about the fact that I am standing again, which is very nice of them," Mr Whan said.

"And I hope that converts into votes for me, but we'll wait and see."

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Mr Whan was called up to run for Labor after the party's first pick, former Raiders captain Terry Campese, withdrew after a series of damaging media stories.

Mr Whan, the son of former federal Eden-Monaro member Bob Whan, said there was a tendency for voters in the seat of Monaro to back a member who would be in government.

"Despite, you know, a very late poll showing Labor ahead, I don't think that people are seeing it as being something that's a foregone conclusion by any means," he said.

Monaro is a huge 20,500 square kilometre NSW electorate to the south-east of the ACT; while Queanbeyan is its largest population base, the seat extends south to the Victorian border.

Mrs Overall said earlier in the afternoon she had heard plenty of positive feedback on the campaign trail and through a busy pre-poll period.

"And the thing that I would say is the most common theme: people acknowledging just how much I've done, the solutions that I've been able to provide, the outcomes that I've delivered in a relatively short period of time having only been in the role for 12 months," Mrs Overall said.

In the year since she won the seat at a by-election, Mrs Overall, the first woman to hold the seat, said she had driven almost 53,000 kilometres across the electorate.

"So the lovely thing is that people have recognised that they know how much I've been out and about and doing the job and yeah, delivering those outcomes," she said.

"To do that in 12 months, I think bodes well for what I can do in a full term of government."

Mrs Overall said voters had told her they had supported her the first time at the byelection she won after the resignation of former Nationals member John Barilaro, and were prepared to do it again.

"So I certainly hope that translates into votes, but it is a wonderful, positive feel out here on the ground today," she said, handing out how-to-vote cards at Queanbeyan South Primary School.

At the February 2022 by-election, Mrs Overall took 45.96 per cent of the first preference vote, despite a swing away from the party.

The Labor candidate, Bryce Wilson, took 31.95 per cent of the first preference vote.

Mr Barilaro took 52.31 per cent of the first preference votes at the 2019 NSW state election in the seat.