Chasing just 152 for victory, the Black Caps looked on the verge of defeat after a stunning bowling spell from Mitchell Starc. Cricket-goers planning on a wild night of celebrations feared they might have to prepare for a wake.
But when Kane "Steady the Ship" Williamson smashed a six to seal the historic win, the crowd went hysterical.
"That was nail-biting stuff, nerve-shattering stuff. I was not at all sure at the end there," Aucklander Nathan Koppens told the Herald on Sunday.
"We got the close game people were predicting but no one said it would be a low-scoring thriller. But mate, I could not be prouder of our boys for holding it together. Kane Williamson is a legend."
Karen Charlton, an Australian who supports the Black Caps, gushed: "I could hardly watch, it was that emotional."
She proudly revealed she had shed tears of joy for the Black Caps.
There were heroes all round - including swing bowler Trent Boult who claimed a five-wicket bag and McCullum, who braved an arm injury to smash a 21-ball 50.
"We didn't see many runs," said Tauranga's Anthony Green. "But I've got to say, at the end there, that was the most exciting game of cricket I've seen."
All week Kiwis had heard that this was the most-anticipated cricket game to be played in New Zealand for 23 years; since the cricketers suffered a heart-breaking loss to Pakistan in the 1992 Cricket World Cup semifinals.
And when the big day finally arrived, the 48,000 packed into the ground were engrossed from the opening ball of the game.
Excitement levels were high on the fan trail leading from central Auckland to Eden Park, with thousands of fans opting to walk to the suburban venue.
When Tim Southee delivered the first ball of the match the roar that went up around the ground was one usually reserved for a hat-trick. It was a wide.
Every dot ball and piece of good fielding was roundly applauded.
And the crowd loved controversial Australian motormouth and opening batsman David Warner. Sports teams from across the Tasman always need a villain - and Warner fits that mould perfectly.
The boos rippled around the park as the scrappy left-hander took strike.
And it wasn't long before an expletive-ridden chant was directed his way.
Warner responded in kind, with his bat. But the fight was short-lived and the wickets started tumbling.
Three for Trent Boult, four, then five. What seemed like the entire Western Stand raised their arms and bowed their heads. "We are not worthy," they chanted.
And once McCullum got going with the bat - the Black Caps were chasing 152 for victory - the chant was a bit more imaginative: "You're worse than England," the crowd decreed.
Cricketing shirts of yesteryear were the outfit of choice, the beige brigade almost outnumbering the orange shirts worn by those trying to catch a share of up to $1 million in the Tui Catch-A-Million competition.
Others dressed in more formal attire, including David Kidd and Chris Black who looked resplendent in their candy-striped London-New Zealand Cricket Club blazers.
Watch: Black Caps v Australia at Eden Park
Kidd, a lawyer, travelled from Hong Kong to be at the game and said the competition between the transtasman rivals was unparalleled.
"We love each other, we hate each other, or is that the wrong order? But it's fantastic, it's a great rivalry.
"And we've waited a long time for a New Zealand cricket team like this. It's payback for all those times that we've been a little bit despondent about the way in which the team's been playing. Suddenly, in the last 18 months, they've been paying us back richly."
On a historic day for New Zealand cricket, not all the applause was reserved for the wickets taken and runs plundered by the Black Caps.
One of the biggest ovations was reserved for New Zealand cricketing legend Martin Crowe who appeared on field in the change of innings to be inducted into the International Cricket Council's Hall of fame.
The master batsman, who is battling cancer, was clearly touched by the standing ovation he received from the appreciative crowd.
"It's so fitting that this induction should be at Eden Park, a home where I made my international debut back in 1982, and where my parents came to watch for nearly 40 years together," he said.
"I'm deeply moved, and will remember this day for the rest of my life."
For more coverage of the Cricket World Cup from nzherald.co.nz and NZME check out #CricketFever.
