He was the fourth-highest wicket-taker last season, snaring 19 at an average of 26.68 and strike rate of 17 for the Mumbai Indians, so his $60,750 pay packet will get a big boost in the 2018 auction.
McClenaghan said a lot had happened since he was offered an NZC contract in late June.
"Some new playing opportunities have arisen in the past few weeks, which mean my circumstances have changed," he said.
"I'm very grateful for the respect, understanding and goodwill that has underpinned my request to be released from my NZC contract.
"I've worked closely with NZC throughout the process, while also making it clear I still harbour ambitions of playing for New Zealand in the future."
NZC high performance manager Bryan Stronach said he respected McClenaghan's decision to pursue a pathway in which he has experienced considerable success.
"We have to recognise that, as the T20 game matures, specialists will want to explore the different opportunities that become available and I think Mitch's case is symptomatic of that," he said.
"This agreement has been reached amicably and mutually; all parties understand the change in Mitch's circumstances and he is released from his contract with our best wishes."
Last year, players signed base New Zealand deals valued at between $83,000 and $205,000, and if selected, earned match fees ranging from $8495 per test, $3682 per ODI and $2407 per T20.
McClenaghan has played 48 ODIs and 28 T20 games for New Zealand, and will remain eligible for national selection.