The New Zealand Inspector-General of Intelligence and Security, Cheryl Gwyn, will investigate complaints that the Government Communications Security Bureau 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.
Cheryl Gwyn says she will also bring forward and expand her review and audit of the Bureau's procedures and systems, to ensure it is complying with the law.
The reports were met by a muted response in Polynesia but former Solomon Islands government officials say the New Zealand practice was unacceptable.
The New Zealand foreign minister, Murray McCully, has not discounted that some of the information was fabricated.