Five men have been charged under the Prostitution Reform Act over allegations involving a minor.
Northland police are investigating after a complaint received in February.
A 35-year-old man was arrested and is facing a significant number of charges relating to sexual offending.
He is next due to appear in the Kaikohe District Court on August 11.
"As a result of further inquiries by police since February, four more men have been arrested and charged in relation to this investigation," Detective Inspector Dene Begbie, Northland district crime manager, said.
The men, aged between 36 and 66, all face charges under the Prostitution Reform Act (2003) and are appearing in the Kaikohe District Court.