He had contemplated being available for the one-day part of New Zealand's tour of England in May and June but couldn't envisage himself playing next summer.
"If I had gone to England, it would have been for selfish reasons and I didn't want to stand in the way of someone else getting an opportunity. I have also had my time with Auckland and I would hate for a young player to miss out at my expense.
"The fact is I'm 36 and there's really no point hanging around for the T20 world cup in a year's time and I won't be around for the next [ODI] World Cup."
There had been concerns he might not have been around for the recent one. Mills has struggled with injuries at various times throughout his career, even missing the 2007 World Cup and returning early from the 2011 instalment, and he spent almost as much time on the treatment table at the Unisports Clinic as he did with his family.
He had five operations and plenty of muscle tears and feared he might have put his 2015 World Cup in jeopardy when he picked up a groin injury on the Pakistan tour late last year.
"One of the things I'm most proud about is to come back from all of those injuries," he said. "It takes its toll physically and mentally.
"When I had knee surgery, I wrote down some goals and on top of the list was to become the world's No 1 ODI bowler. So to achieve that was brilliant."
Mills still hopes to be involved in cricket. Exactly what, he's not sure, but he's acted as something of a mentor to the younger bowlers in all of the teams he's been involved in.
He's also involved in an artificial grass business.
"It feels like I'm leaving school again," he said. "I'm not sure what I'm going to do. It wasn't an easy decision [to retire] but I'm really content.
"The future of the New Zealand team is bright. I think they can achieve some pretty special things. I feel that they're only going to get better and that's quite scary, because the bowling group is already achieving great things in both tests and one-dayers. It's going to be an exciting time for New Zealand cricket."
Kyle Mills
Age: 36
Tests: 19 matches (44 wkts @ 33.02)
ODIs record: 170 games (240 wkts @ 27.02)
T20s: 42 matches (43 wkts @ 28.55)
Mills made his international debut against Pakistan in 2001, with his last match being January's ODI against Pakistan in Wellington when he snared 2-29 off his 10 overs.
He was the world's No 1-ranked ODI bowler in 2009 and he's still 27th even though he's had limited game time recently.