The Inspector-General of Intelligence and Security, Cheryl Gwyn, will investigate complaints that the Government Communications Security Bureau (GCSB) intercepted the communications of New Zealanders working or travelling in the South Pacific.
The claims were made in recent reports based on documents released by the American whistleblower Edward Snowden.
They allege the GCSB conducted mass surveillance in the region.
Ms Gwyn said she would also bring forward and expand her review and audit of the Bureau's procedures and systems, to ensure it was complying with the law.
Prime Minister John Key says the inspector-general's role is to satisfy the public about the agency's activities and he's not concerned about the inquiry.