Fiji's 12-4 lead over New Zealand threatened an upset in the teams' Women's Rugby League World Cup opener at McDonald Jones Stadium in Newcastle.
The Kiwi Ferns recovered to win 18-12, but co-captain Georgia Hale said the result was fortunate.
"It was just luck in the end," Hale said.
Stacey Waaka scored twice, including a try just before half-time, while Leianne Tufuga crossed three minutes from full-time.
Zahara Temara added two late penalty goals to secure the victory.
Hale played 50 minutes, making 32 tackles and running eight times for 69 metres.
She began at hooker, as she had for the Titans that season, before shifting into the middle as a forward.
"They were relentless, they kept coming, they played like they had nothing to lose, and they tested the waters for sure," Hale said.
She said New Zealand lost control through ill-discipline and untidy play, falling short of its aim to set a physical tone.
Coach Ricky Henry said New Zealand made 50 more tackles than Fiji, leaving the Ferns' "petrol tank" low.
"But again, I felt like we fought the way back, we found a way to get back into the game, and found a way to win the game," Henry said.
He praised Fiji, playing its first World Cup and featuring several NRLW players: "It might be Fiji and their first time in the World Cup, but they're a good team."
New Zealand won the first three Women's World Cups and are considered Australia's main challengers behind the three-time defending champions.
The Kiwi Ferns face France at Christchurch's One NZ Stadium on Sunday at 1pm AEST/Queensland time. France began with a 58-4 loss to Papua New Guinea.