On the back of some outstanding Super 12 form, Nonu made his Test debut for the All Blacks on 14 June 2003, starting at centre in a 15-13 loss to England.

Nonu missed selection for the 2003 Tri Nations, with the selectors preferring Umaga, Aaron Mauger and Daniel Carter in the midfield.

He scored his first Test try against Canada and was generally impressive on attack and easily breaking the line and his big stature was intimidating to the opposition.

However, question marks over his defensive game and inexperience meant he was not selected for the knockout stage of the tournament despite an injury to Umaga.

Wellington Lions captain Umaga was rested during the 2005 NPC, and in his absence Nonu was promoted to the captaincy of the team.

In 2006 Nonu was ruled out of the Tri Nations squad due to injury, Mils Muliaina being chosen to take his place.

Due to his absence from the All Blacks Tri Nations squad, Nonu was able to play every game with the Wellington Lions in the Air New Zealand Cup, which greatly helped them.

Nonu missed out on selection for the 2007 Rugby World Cup, with the selectors preferring Aaron Mauger, Luke McAlister, Conrad Smith and Isaia Toeava in the centres.

Nonu's performances following his return from his Black Rams sabbatical were met with poor response[citation needed] and subsequently led to his exclusion from the match-day 22 for the France test series.

Following Williams' departure to Japan and then the NRL, Nonu played all but one of the remaining tests as second five-eighth, except against Scotland where he came off the bench.

After struggling to find a Super Rugby team for 2014, (where all 5 New Zealand franchises initially stated they weren't interested in signing him),[15] Nonu eventually turned down a lucrative offer to play for French Top 14 side Clermont, to return to the Blues for another season.

In doing so, he made himself available to continue playing for the All Blacks throughout 2014 and ultimately gain selection for the Rugby World Cup the following year in England.

On 20 December 2014, it was announced Nonu would be joining Top 14 side Toulon after the 2015 Rugby World Cup on a two-year deal.

[17] Nonu was selected as the starting inside centre for the 2015 Rugby World Cup, he played in nearly every pool game.

Nonu played every knockout match and scored a 50m solo try to help the All Blacks beat Australia 34-17 in the final.

[19] Major League Rugby announced in October 2019 that Nonu would play for the San Diego Legion in the 2020 season.