Mr Luxon pulled the extraordinary move during a marathon caucus meeting of his National Party MPs in Wellington on Tuesday.
After a debate characterised by MPs as "good, honest" and "robust", he emerged alongside his deputy Nicola Willis to announce his MPs supported him staying on.
"I moved a formal motion of confidence in my leadership. That motion was passed, confirming what I have been saying: I have the support of my caucus as their leader," he told journalists in Wellington.
However, crucially, the party is keeping the vote tally a tightly guarded secret, meaning it is not known how widespread internal dissatisfaction is.
Mr Luxon took the centre-right National into government in 2023, winning the election and forming a coalition with the NZ First and ACT parties.
However, the former Air New Zealand chief executive has never been well-liked by Kiwis and both he and his party have bled support since.
Instability has bubbled over in recent days following a NZ Herald report that Mr Luxon "ghosted" his party whip who tried to inform him of growing concerns.
On Monday, Mr Luxon labelled that probably "five people that are moaning" - a shift from previous outright denials of trouble.
In Question Time on Tuesday, Labour leader Chris Hipkins asked Mr Luxon whether he had the unanimous support of his partyroom, to which he replied "absolutely".
Outside the chamber, Ms Willis described the confidence vote as an "emphatic" majority.
"One for all. All for one. When the caucus by majority have confidence in the leader then we all stand together backing the leader," she told journalists.
Mr Hipkins has challenged Mr Luxon to show his hand and release the vote count, which appears unlikely as it would show the scale of his MPs' dissent.
The confidence powerplay came about after months of polling drift for Mr Luxon and National, underscored by a bombshell survey from TVNZ-Verian on Sunday.
It had Mr Luxon as the preferred prime minister of just 16 per cent of respondents - Â behind Opposition Leader Chris Hipkins - with net personal approval of negative 23 per cent.
On those numbers, if an election - which will be held on November 7 - were held last week, the left bloc led by Labour would have triumphed.
Whether Tuesday's vote has changed the dial on Mr Luxon's political future was hotly debated in the aftermath of proceedings.
Winston Peters, the leader of key coalition support party NZ First, told journalists the leadership vote was "very bad" and would be followed by more instability.
"There's always inevitable consequences. This is not the first time it's going to happen, you see," he said.
Veteran political journalist Barry Soper said the vote was unprecedented in recent times and a "big risk".
"I can't remember any of the prime ministers I've covered putting themselves to a vote of confidence ... they didn't need to," he said.
While Mr Soper said he thought it "puts an end to everything before November", other commentators disagreed.
Radio NZ deputy political editor Craig McCulloch summed up the prevailing mood by saying the confidence vote bought the prime minister more time.
"The only thing that is going to end this situation is if Christopher Luxon can turn the polling around and if he can bring National's polling up from the low 30s," he said.
In a swipe at journalists, Mr Luxon considers the matter a "media soap opera" and now closed.
"Caucus has answered clearly and decisively. It has backed my leadership," he said.
"If the media want to keep focusing on speculation and rumour, I am not going to engage.
"That matter is now closed and I won't be commenting further on it."
