Sam Davies, on his first international start, kicked 12 points to help secure the win.
Wales started their two-Test summer tour with a win as Alex Cuthbert's first-half score and a late penalty try sealed a fully deserved 24-6 victory over Tonga.
On his first international start, fly-half Sam Davies ended the game with 12 points, Cuthbert's impressive try the stand-out moment of a game in which both sides made errors.
On a cool night at Auckland's Eden Park, Wales started in impressive fashion. Robin McBryde's side had plenty of ball, with Cuthbert the main danger to the Tongan defence.
The Cardiff Blues winger had two scores ruled out by TMO Ben Skeen, but Cuthbert was not to be denied on a third occasion. After Davies had put Wales ahead with a penalty, a loose kick from the Pacific Islanders saw Wales run the ball back with intent.
Gareth Anscombe was the creator, putting Cuthbert into space who chipped through and collected his own kick to score. It was a superb finish, but with Davies missing two kickable penalties and the conversion, Wales weren't as far clear as they should have been.
It allowed Sonatane Takulua to put Tonga on the board with a penalty, and an 8-3 lead was one Wales held on to until the half-time whistle.
McBryde's men should have been further clear, Davies' misses on goal proving costly, and the start of the second period saw Cuthbert replaced by Cory Allen as heavy rain came down.
Wales' try scorer had taken a first-half knock and as the game restarted, the rain fell down to make life more difficult for both teams.
Takulua and Davies exchanged further kicks at goal, but the error count was high as kicking dominated the game.
A huge hit from David Halaifonua on Allen shook Eden Park to its core, and McBryde introduced Ellis Jenkins, Ryan Elias and Owen Williams - a blood replacement for namesake Scott - on the hour mark in search of some inspiration.
The game was still scrappy, but Davies' third penalty gave Wales some breathing space. Takalua was then unable to find the mark with a kick of his own and with that, the game was up.
Davies put the nail in the Tongan coffin with another well-struck penalty and there was still time for Wales to add gloss to the scoreline.
A huge forward surge saw Wales head towards the line, referee Nick Briant awarding a penalty try which under World Rugby's new laws, was converted automatically without the need of Davies' boot..