He was picked by Kings XI Punjab for the inaugural edition of the Indian Premier League in 2008, but did not play in any of the matches.

Although New Zealand lost the inaugural T20I by 44 runs, Mills made an impact picking up 3/44 on his T20I debut after opening the bowling with Tuffey.

He was initially out for at least 12 months but after an operation on a patella tendon and a winter of rehabilitation, he worked his way back to fitness to take part in New Zealand's tour of South Africa in November–December 2007.

[31] Due in part of the absence of Shane Bond, who signed to play in the Indian Cricket League, and Mills' continued good form, he maintained his place in the ODI side.

Mills became a frontline bowler for New Zealand in limited-overs matches from 2008 in and was groomed to fill the void left by Bond.

[32] He dismissed Alastair Cook, Michael Vaughan, Andrew Strauss and Kevin Pietersen within his first seven overs of his spell on the final day of the test match whereas England were given a brisk target of 300.

He was also a member of the New Zealand side which emerged as runners-up in the 2009 ICC Champions Trophy Final, after losing to Australia in South Africa.

[40] However, after featuring in just three group stage matches he was ruled out of the remainder of the 2011 World Cup tournament due to an injury.

[44] In November 2013, he served as a stand-in captain on his captaincy debut in the third and the final ODI against Bangladesh which New Zealand lost.

[47] He was appointed as the captain of the national team for the limited overs tour of Sri Lanka in 2013 replacing Kane Williamson.

[56] In 2010, he was banned from bowling in a warmup match for at least half an hour after breaching Law 17.1 for pitching a practice delivery on the popping crease.

[57] He was fined by the International Cricket Council for breaching the ICC Code of Conduct during the quarter final match between South Africa and New Zealand in the 2011 World Cup.

He was charged for exchanging words with South African batsman Faf du Plessis following the run out of AB de Villiers.