Labor will analyse its win in the Fannie Bay poll but Northern Territory Chief Minister Natasha Fyles says by-elections are always tough for sitting governments.
Labor survived a big swing to the Greens and Country Liberal Party in Saturday's count and has claimed victory for Brent Potter.
Ms Fyles has also pointed to a low voter turnout after the CLP's Ben Hosking received the most first preference votes.
On a two-party basis, Mr Potter was ahead by 148 votes, enough for Labor to claim victory and for Mr Hosking to concede.
"Preferences from the Greens got Labor over the line but the 16 per cent swing away from Labor is a message they cannot ignore," Mr Hosking said in a Facebook post on Monday.
"I will continue to fight for the people of Fannie Bay over the next two years as we head towards the 2024 general election."
Mr Fyles said Mr Potter would be an "incredible local member".
"He will be out there working hard for that community and engage with that community," she said.
"By-elections are always tough for governments but we certainly will analyse the result.
"We don't take anything for granted."
Mr Potter will join the Legislative Assembly after working as a government adviser and previously serving in the army.
He will represent an electorate where the past three local members have all gone on to be NT chief ministers.
The CLP's Marshall Perron first took the seat in 1983 after his previous electorate of Stuart Park was abolished in a redistribution.
He became chief minister in 1988, serving until 1995 when he quit parliament as it began debating voluntary euthanasia laws, something he strongly supported.
Labor's Clare Martin then won the seat in a by-election before becoming opposition leader in 1999 and chief minister when the ALP won office in 2001.
Ms Martin served until 2007 and quit politics at the 2008 election, when Mr Gunner retained the seat for Labor.
After Labor lost office in 2012, Mr Gunner went on to become opposition leader in 2015 and chief minister from 2016, when the party won a convincing majority.
He stepped down in May after leading Labor to another win in 2020 when the party lost four seats.
