The Walk Free report identifies cases of forced labour, commercial sexual exploitation of children, and forced marriage in the Pacific.
The report, Murky waters: A qualitative assessment of modern slavery in the Pacific region, said exploitation was fuelled by widespread poverty, migration, and the abuse of cultural practices.
Senior researcher Elise Gordon said they had conducted interviews with law enforcement officers, victim support workers, policy and advocacy stakeholders, and people in the education and training industry in New Zealand, Australia, Fiji, Papua New Guinea, Samoa, the Solomon Islands, Tonga, and Vanuatu.
"We have heard reports of signs of modern slavery among migrant workers in the construction industry, stemming from increasing foreign investment in Pacific Island communities," Gordon said.
"Also fishing, a major industry in the region, brings with it a poor track record as being notorious for forced labour and human trafficking for labour exploitation."
Modern slavery was likely to increase as climate change exacerbated poverty and migration, Gordon said.
The report was released in the same week the first person to be convicted of slavery in New Zealand was sent to jail.
It said only a third of 54 Commonwealth countries had criminalised forced marriage and 23 nations had failed to criminalise the commercial sexual exploitation of children.
New Zealand did not do enough to stop modern slavery through its supply chain, the report stated.
Walk Free director Grace Forrest said the introduction of a modern slavery Bill should be among the New Zealand government's top priorities after the election.
The Australian government passed a Modern Slavery Act last year.