North had been warned about his form by defence coach Shaun Edwards in the build-up to the game and responded by demonstrating his quality and power as Wales scored three unanswered tries in a hard-worked win.
RNZ reports Wales led 8-6 at half time.
Jamie Roberts clinched the game with Wales' third try in the 78th minute.
Ireland's New Zealand coach Joe Schmidt said his side paid a high price for a yellow card handed to first five Johnny Sexton which saw Wales score 10 points in six minutes either side of half-time.
Victory ensured Wales will stay in the top eight of the World Rugby rankings and avoid a potential horror draw for the next Rugby World Cup in Japan.
They had lost their previous Six Nations clashes against Scotland and England and were in danger of slipping down the rankings.
The result also ended any Irish hopes of securing a third Six Nations title in four years.
England can secure the title if they beat the Scots at Twickenham tomorrow.