A three-try burst in seven minutes shortly after the break brought the Ferns back within four, before centre Mele Hufanga went the length of the field to seal an incredible 22-20 comeback win.
In a tense start, both sides produced trysaving tackles in the opening 10 minutes.
First, Samoa's Destiny Brill made a strong run from the ruck, but Ferns fullback Apii Nicholls knocked the ball free.
The Ferns looked to cash in, as Shanice Parker took a cross-kick clean and just needed to grass the ball, but Jessica Patea's cover hit jolted it out of her grasp.
With yet more territory, Samoa again took the direct route, with Shalom Sauaso coming off the pine and absolutely bulldozing her way to the line with her first touch, smashing her way through five defenders to put her side on the board.
Another denial came just moments later, with Destiny Mino-Sinapati latching onto a high ball and getting over the chalk, but a horde of ferns kept her from grounding.
There was no repelling Sarina Masaga though, as the centre showed slick footwork to squeeze though the Ferns defence for Samoa's second.
Just as the Ferns were looking to get bak into the contest, Mino-Sinapati sent the crowd into raptures, as she snatched a Patricia Maliepo cross out of the sky and streaked 90 metres, with just enough gas in the tank to outstretch the cover.
Things then began looking dire for the home side, when Masaga wove through tackles and linked with a rampaging Tavarna Papalii to put Samoa in a commanding position at half-time, sending the Ferns to the sheds shellshocked at 20-0.
The Ferns managed to pull one back not long after the break, when Parker took a deft chip ahead by halfback Raecene McGregor to finally get the home side on the scoresheet.
Another try from the next set had the Ferns right back in the contest, with Ashleigh Quinlan slicing through some tiring defence to suddenly reduce the margin to 10.
The comeback was all but complete, when a grubber kick ahead saw a scramble by the posts, with the ball eventually landing in the arms of Alexis Tauanea, who slammed it over the chalk, as the Ferns roared back with a 16-unanswered point blitz.
The rampant Ferns looked impossible to stop and only a Parker error in trying to ground the ball prevented them from squaring the scores.
The tide then officially turned in cruel fashion for Samoa, who were hot on attack, but their fifth-tackle kick was snaffled by Hufanga.
Still 90 metres from the try-line, she hustled down the left flank, showing just enough toe to avoid the ever-closing cover, and Maliepo slotted the sideline conversion to put New Zealand in the lead for the first time.
Samoa had one last shot in the final moments, but Nicholls again stepped up to snuff out their last opportunity, as the Ferns closed out a pulsating clash.
