The Cook Islands Trade and Labour Office says people coming to the country intending to work, must have the correct documents or they can't stay.
The warning follows the discovery of a scam by a Nadi-based consultancy firm, Perfect Match Introduction Fiji limited, which offers to compile the necessary documents for a Cook Islands work permit.
At least two men from Fiji, who had each paid 660 U.S. dollars to the company, were forced to return home from Rarotonga because they didn't have the right papers.
The director of Trade & Labour, David Greig, says there is a strict policy in place between his office and immigration for foreign employees coming into the country.
"That contract has to be endorsed and approved by myself to make sure that no future disputes will happen. But you know such scams like this, such scams like this, this is my first knowlege. I haven't heard of any such scam of this nature."
Mr Greig says before potential employees arrive, they should contact immigration which is responsible for ensuring contractual employment is in place, before they issue any work permits.
Meanwhile, a Fiji Police spokesman Mesaki Koroi says its the first employment immigration scam they've heard of, that's targeting the Cook Islands.