NZSIS undertakes a range of functions relevant to New Zealand's security. These include:
- Collecting, analysing and reporting on intelligence relevant to New Zealand's security
- Providing protective security services including advice about personnel security, information security, physical security and national security risks
- Co-operating with Government Communications Security Bureau, New Zealand Defence Force and New Zealand Police to facilitate their functions and co-operating with other agencies to respond to an imminent threat to life or safety
In exercising its functions NZSIS must act in accordance with the law and human rights obligations, independently and impartially, and in a manner that facilitates democratic oversight.