Mr Key signed the agreement yesterday in Brussels with Nato Secretary-General Anders Fogh Rasmussen. Nato, the North Atlantic Treaty Organisation, is a military alliance between the United States and Canada and 26 European countries.
Mr Key said the engagement between New Zealand and Nato had developed considerably over the past 10 years, mainly through involvement in Afghanistan.
"This arrangement is a move to capitalise on this engagement, and formalise the current more substantive relationship that exists between Nato and New Zealand."
The deal with New Zealand sets out steps to boost co-operation in fields such as cyber-defence, disaster relief, crisis management and training.
New Zealand has about 140 troops in Bamiyan province in Afghanistan while Australia has 1550, the largest non-Nato contingent in the 130,236-member international security assistance force. Both are due to withdraw next year.
Defence Minister Jonathan Coleman said the agreement put together in a non-binding way a framework for future engagement instead of "drifting off" after Afghanistan.
DEAL STRUCK
What the Nato agreement means:
* Greater political consultation.
* Common approaches to security issues such as cyber threats, terrorism, piracy.
* Continued intelligence sharing.
* Enhanced inter-operability.
- Additional reporting: AP