The All Blacks raced in for four tries in the first 33 minutes and led 29-3 at the break, then went cold for 20 minutes before finishing off their Pacific neighbours 41-10 with two late tries in the first of 48 matches at the seventh World Cup.
Fullback Israel Dagg and winger Richard Kahui scored two tries each and Jerome Kaino and Ma'a Nonu also crossed for well-deserved tries, with Sonny Bill Williams providing plenty of offloads for the All Blacks backline.
"There was some good patches. I thought we brought the physicality," All Blacks skipper Richie McCaw said. "There's some good bits there. It's a start — that's all we can look at it as."
Replacement prop Alisona Taumalolo scored Tonga's try in a second-half that will give his team some confidence in their remaining games in Pool A.
"The ABs started very well. Every time we made mistakes, they scored points," Tonga captain Finau Maka said. "The boys came out in the second half firing — I thought we defended well and showed that we can ... score a try against the best team.
"In the World Cup, momentum is important. We take a lot of positives from this game."
It was crucial for the home team to open with a win after seven years of preparations in New Zealand, where the public will grow increasingly uncomfortable until the All Blacks break a long drought and win a second World Cup title. The New Zealanders haven't won since they hosted the inaugural tournament in 1987.
Massive crowds packed the downtown harbour front areas in New Zealand's biggest city, with ferries and trains unable to handle the tens of thousands of spectators who flooded the streets.
The All Blacks weren't the only team to open with a bang.
The Australians also came out swinging — albeit among themselves. Reports of a punch up during an intense, opposed Wallabies' practice were acknowledged by centre Anthony Fainga'a. The No. 2-ranked Australians, who beat the All Blacks two weeks ago to claim the Tri-Nations title for the first time in a decade, open their campaign Sunday afternoon against Italy in Auckland.
"It's training and there is 30 guys in a team and only 22 guys can put on (test squad) jumpers, so there is always a few punches and some words at training," Fainga'a said. "Having guys chasing right behind you makes you become a better player.
"It also keeps you on your toes the whole time. It creates a healthy culture," he added. "We train how we play."
There are four matches Saturday and another three on Sunday in a frenetic weekend.
Scotland and Romania get play under way at Invercargill in Pool B, before Fiji and Namibia meet at Rotorua and the big night match at Dunedin's new covered stadium between England and Argentina, the teams which finished second and third in 2007.
Jonny Wilkinson, who kicked England to victory in the 2003 World Cup, is back at No. 10 and will be closely marked by Pumas captain Felipe Contepomi in a match that is destined to feature some heavy engagements in the scrum.
France coach Marc Lievremont is so desperate to avoid a repeat of the disastrous opening loss in 2007 that he took the unusual step of publicly rebuking his squad for its attitude in a laborious practice session.
"I could do without that," he said, referring to France's defeat to Argentina in its opening match as tournament host four years ago. "What's for sure is that we are taking this first match seriously. If we don't do things properly they have the ability to cause a lot of problems."
To mark the 10th anniversary of the 9-11 attacks, the U.S. Eagles will attend a church service Sunday morning, observe a minute's silence before kickoff and wear black armbands during their evening match against Ireland.
"In the heat of the moment the emotion is going to hit," said loosehead prop Mike MacDonald, who will set a U.S. record for most test caps when he runs out on Sunday in his 63rd test. "It will hit people in different ways."
Defending champion South Africa will bring the opening weekend to a close with a challenging Pool D match against Wales.
Springboks coach Peter de Villiers announced his squad Friday, unveiling the most experienced team ever with a combined 815 test caps. Wales coach Warren Gatland acknowledged that experience but said his lineup, with its 496 caps, would measure up.
"That's definitely their strength, their experience, and they rely on that and are a tough team to beat," said Gatland, who has put his faith in 22-year-old flanker Sam Warburton to lead the Welsh team. "It does help having some experience. I think we've got a nice mix of some talented youngsters with some experience as well."