The party saw a dramatic fall in support on election night, with preliminary results showing Labour's share of the party vote has fallen by almost half.
"Democracy can be incredibly harsh," outgoing Prime Minister Chris Hipkins told party supporters in the Lower Hutt Town Hall on Saturday night.
Labour's caucus will meet on Tuesday, where they will start shifting their focus to what happens next.
It became obvious early on Saturday night the massive red wave had receded - leaving a devastated party in its wake.
Supporters told RNZ they were "gutted", "very upset" and "a little bit depressed".
Support for Labour was always going to fall, after it reached never-before-seen heights in 2020.
But the preliminary election results showed it had collapsed to just under 27 percent - bringing brutal consequences for Labour's caucus.
Twenty-one of the party's MPs lost their jobs on Saturday night - including former ministers Michael Wood and Nanaia Mahuta who had been in parliament for 27 years.
Mahuta had held the seat of Hauraki Waikato for 15 years, but lost it to Te Pāti Māori's Hana-Rawhiti Maipi Clarke.
"I have no regrets and I'm looking forward to the next chapter of my life," Mahuta said.
All 14 of the safe National seats Labour flipped red in 2020 have gone back blue.
That means it is game over for MPs such as Sarah Pallett in the Christchurch seat of Ilam.
"We tried as hard as we could and things didn't worked out as we'd hoped."
Leading into the election, some of Labour's senior MPs looked to be at risk of not making back to Parliament on the list.
But the party's poor performance in the electorates allayed those concerns.
Instead, more than half of Labour's 2020 intake of MPs won't return - including Angela Roberts, Anna Lorck and Naisi Chen.
"Very devastated, obviously there's the specials which tend to be in our favour. It's all a very devastating result for us," Chen said.
The exact make-up of Labour's new look caucus won't become clear until after the final result has been confirmed.
And even then - some of the party's old guard - including Grant Robertson and Damien O'Connor - could choose to move on, allowing room for fresh blood.
Glen Bennett's list ranking could see him make a comeback.
"If there is a chance to serve on the list ... then I'll absolutely do that."
The 500,000 yet-to-be counted special votes could also change the outcome in marginal seats.
Labour's Phil Twyford is just 30 votes behind in Te Atatu and in Nelson, there are just over 50 votes separating Rachel Boyack and National's candidate.
They both have to win the electorates to return to Parliament.
"It will be quite a long wait for the next three weeks as we wait for the special votes to come in."
Labour's dire result means the party is set to bring in just two new MPs: Reuben Davidson and Cushla Tangaere Manuel.
"It's bittersweet because I'm really aware of the huge shoes I'm stepping into to represent the people of Christchurch East but I had hoped to be doing it as part of a labour government," Davidson said.
The pair will join Labour's caucus at an unenviable time - as it enters the political wilderness.
The party will have already begun pondering what went so wrong.
Such reflection will inevitably present questions about leadership.
"Decisions about the future are for another day," Hipkins said, when asked about his plans on Saturday night.
That day will soon come.
Labour's caucus will meet at Parliament on Tuesday to welcome its new additions and farewell those who aren't coming back.
From there, the MPs who survived the blue wave will start picking up the pieces.
