Second five-eighth Michael Collins and winger Fa'asiu Fuatai scored doubles and fullback Lolagi Visinia, winger Leroy van Dam, lock Scott Scrafton and flanker Jordan Manihera also crossed. The four-time champions play their next game on Monday against Australia, who lost their opening match to Ireland 19-15.
Fiji were reduced to 14 men in the 30th minute when Sevanaia Galala was sent off for a tip tackle. Six minutes later they had just 13 men on the field when Nasoni Kunavore was yellow carded.
It got even worse after halftime when Sunia Tamani and Timilai Rokoduru were both also sinbinned for a swinging arm and a late tackle respectively.
That left them with 11 men for a couple of minutes as New Zealand ran in another try by simply spreading the ball wide. Just as Kunavore re-entered, Fiji were left with 11 men once again when Viliame Rarasea become the second Fijian sent off, for a high tackle.
New Zealand made the most of the tiring Fijian defence scoring four tries in the final 25 minutes.
NZ Under-20 59 (Fa'asiu Fuatai 2, Michael Collins 2, Ardie Savea, Lolagi Visinia, Leroy van Dam, Scott Scraftons, Jordan Manihera tries; Tayler Adams 2 cons, 2 pens, Sheridan Rangihuna 2 cons) Fiji Under-20 6 (2 pens).
NZ 59
Fiji 6