Ardern announced her shock resignation on Thursday, citing exhaustion after five and a half years in the job.
Her surprise exit - not known to her partyroom until just hours before - set Labour MPs racing to find a replacement as party leader and prime minister.
Hipkins, the police and education minister and a trusted ally of Ms Ardern, emerged as the consensus candidate in the hastily-convened leadership race, which will be ratified at a partyroom meeting on Sunday.
The 44-year-old, who was raised and lives in the downtrodden Hutt Valley to the north of Wellington, said he was honoured and humbled by the endorsement.
"It's a big day for a boy from the Hutt," Hipkins said outside parliament house on Saturday.
"It's an also an enormous responsibility and the weight of that responsibility is still sinking in. But I absolutely take it very seriously and I'm really looking forward to it."
Hipkins stayed tight-lipped on the discussions that led to his unopposed candidacy as Labour leader.
The 44-hour process did not allow grassroots Labour members or the Kiwi public a say, which Ardern justified as crucial to allow government stability.
"The most important thing is that we focus on a process that is swift, that ensures that the team was able to move quickly back to focusing on the issues that matter for New Zealand," Ardern said.
Local media outlets speculated Michael Wood, the transport minister, also considered nominating for the leadership, which would surely have been won by deputy PM Grant Robertson, who instead ruled himself out from contention.
Instead, Hipkins will take the reins for the next nine months ahead of an election Ms Ardern set for October 14.
Labour is narrowly trailing the centre-right opposition National party according to public polls, and the party hopes Hipkins' fresh leadership will re-cast the race in their favour.
The Remutaka MP is a well-liked member of parliament, known for his sense of humour and enjoyment of sausage rolls.
He is Labour through and through, volunteering for the party at a young age, was head boy at his high school and president of his university student union.
After working as an adviser in the Helen Clark government, he entered parliament in 2008 in the same intake as Ardern and Robertson - who was best man at his wedding.
He endured nine years in opposition before emerging as the Ardern government's most senior figures, as leader of the house for the last five years.
He has been thrown difficult jobs - such as COVID-19 minister and police minister - by Ardern when safe hands were needed.
The pair are close friends, taking their young children on play dates outside of parliament.
Hipkins is also a political warrior with an enthusiasm for point-scoring that has led to him overstepping the mark.
His most notable episode for Australians came in 2017, when he used parliament to dig for information on the dual citizenship status of Barnaby Joyce, drawing censures from then-Australian foreign minister Julie Bishop and Ardern in a rare trans-Tasman spat.
Prime Minister Anthony Albanese was quick to congratulate Hipkins earlier on Saturday.
"We had a good chat ... it was very warm," he said.
"There is a Labor government in Australia, a Labour government in New Zealand. Of course that means that we've going to have a good working relationship."
A variety of surveys from NZ media outlets and polling agencies confirmed he was the most popular Labour MP to follow in Ardern's footsteps.
Local media is also reporting Labour MPs may re-think their deputy leader role, currently held by Kelvin Davis, promoting Auckland-based MP Carmel Sepuloni to the job.
Hipkins said decisions on his team would be announced in the coming days.
AAP
