A streaker on the field with six minutes left lightened the mood at the sold out stadium but the last minutes were tense as both teams threw everything into the contest.
"I'm proud to be a Canadian," Crowley quipped afterwards. "This will give the guys a lot of confidence and self belief that they can get across the line. Two or three years ago we would have lost this game tonight."
It was a tough test for the Tongans to front up at the more modest environs of Whangarei after the highs of the opening night at Eden Park.
Canada had the advantage of watching that victory by the All Blacks and lay in wait, fresh and willing to take the Tongans on in their first game of the tournament.
With Japan and France to play in Pool A, Tonga's chances of a victory are fading fast and coach Isitolo Maka was bitterly disappointed afterwards.
"The message was sent out there to play the game in Canada's half and what do we do? Play the game in our half, they get a turnover and score," Maka said.
Playing with the wind, Canada made their intentions clear when winning their first possession - a lineout and maul driving Tonga back with a concerted shove.
Their methods may have been a little more pragmatic than Tonga's - keeping it tight then hoisting it high - but they were no less effective, and in the end that application to a simple game plan won the day.
Canada scored after 15 minutes through lock Jebb Sinclair following good work by flanker Chauncey O'Toole and first-five Ander Monro. Sinclair was the beneficiary following a final thrust by second-five Ryan Smith.
Fullback James Pritchard excellently converted from the sideline.
The Tongans were becoming frustrated and the harder they tried the more mistakes they made. A penalty for offside was gladly taken by Canada and the margin was out to 10 points after 26 minutes.
First-five Taniela Moa, the sometime halfback, sported an elaborate hairstyle and colour which made him hard to miss, especially when he made errors. He may want to blend into the background a little more this week as Moa was the man who should have been setting Tonga's agenda for his coach.
The man outside him, Alipate Fatafehi, was all power, but the Canadians kept working away, sticking to their gameplan of keeping it tight and feeding off errors.
Jason Marshall the tighthead prop, was having a strong game as well as Sinclair and his locking partner Jamie Cudmore.
Their centre DTH van der Merwe - it's not only All Blacks who are known by their initials - and blindside flanker Adam Kleeberger were two others who seemed to pop up at opportune moments.
Kurt Morath missed two penalties for Tonga and with three minutes to go in the half and another penalty for offside, the Tongans decided to go for broke and it paid off, with Siale Piutau breaking through.
After the break, Morath put Tonga level with a penalty, but Pritchard replied straight away to restore Canada's advantage.
Moa's inside ball put Piutau away for his second try and Tonga's weight of possession was beginning to take its toll.
Against the odds, No8 Carpenter scored for Canada with 15 minutes to go to set up an exciting finish.
They turned down a tough kick at goal with 10 minutes remaining, preferring to kick for touch, and it paid off as wing MacKenzie slipped through the defence.
Canada have injury issues with O'Toole replaced in the first half with an ankle injury.
But the Canadians last night looked set to enjoy the moment despite the tight turnaround, skipper Pat Riordan rating the victory as his proudest moment.
With three victories out of three over Tonga at World Cups, the Canadians have form. Now for a different challenge against France.
Canada 25 (Jebb Sinclair, Aaron Carpenter, Phil MacKenzie tries; James Pritchard 2 conversions, 2 penalties) defeated Tonga 20 (Siale Piutau 2 tries; Kurt Morath 2 conversions, 2 penalties). Halftime: 10-7
