Kirwan, 29, made the announcement on Saturday, although he will captain the New Zealand Barbarians against the Australian Barbarians on Friday night.
Kirwan was left out when the All Blacks played Australia in August.
He said he decided to retire as he watched Auckland's semi-final win against Otago.
'I wasn't missing it and thought that was a pretty good sign that this was the time to call it quits,' he said. 'Rugby was my life for 12 years, everything revolved round the sport. I would have been considering this even if I had played in the last few games. I can't give rugby the commitment I need to give it and think it is time to move on.'Reuse content