A whistleblower alerted Immigration New Zealand to the exploitation of 12 Indian workers in the South Island.
A 30-year-old employer was found to have forced staff across his South Island operation to work more than their visas allowed, refused to provide time off and paid them less than minimum wage.
Davinder Singh was convicted yesterday in Nelson District Court on 25 charges of exploiting 12 Indian workers.
His company, Kishan Singh & Son's Ltd, owned Pizza Hut franchises in Gore, Richmond, Blenheim and Nelson, which were on-sold in 2016.
Singh also operated two food stores trading as Ekam Food Marts in Nelson and Blenheim. He encouraged employees on student visas to work more than their visas allowed, then underpaid them.
Others he employed on work visas were only ever paid for 40 hours, despite some working up to 60 hours a week.
One employee was forced to work seven days a week without overtime, while another living in Singh's home was made to cook and clean for him and his family.
Another employee was owed almost $65,000 in outstanding pay.
Singh was sentenced to 200 hours of community service and ordered to pay $150,000 in victim reparation.
Immigration New Zealand assistant general manager Peter Devoy told Morning Report the case came to light after a "brave victim" of the employer stepped forward.
Mr Devoy said migrants should not be discouraged from blowing the whistle on such employers, however, each case would be treated individually.
"If they come forward to us and they are genuine victims, they will not be disadvantaged and we will reset their visa types and give them an opportunity to experience New Zealand as it should be."
Some exploited migrants might be staying quiet in fear of breaching their visa rules, he said.
"Where we see the tip of the iceberg is in these prosecutions. It's very difficult to bring the prosecutions and it is more likely than not that migrants who are being exploited are sucking it up and putting up with it for a period of time," he said.
"They're not familiar with the laws of New Zealand, they're not familiar with the language and they're being told that they may well be, if they don't do what they're being told in the employment situation, then Immigration New Zealand will deport them."
While the case was unfortunate, it did not come as a surprise, Mr Devoy said.
With more cases coming to light on migrant exploitation, the labour inspectorate along with Immigration's investigators were keeping a close on employers hiring migrants, Mr Devoy said.