The ministry's director of public health Caroline McElnay said moving from monitoring to enforcement was a precautionary but necessary approach to keep Covid-19 out of the community.
The fines came after many attempts to contact the workers to encourage them to comply, McElnay said, including providing testing opportunities, reminders, and issuing formal warning letters.
"Border controls are a key tool for stopping the introduction and spread of new cases from overseas and remain central to our elimination strategy, which has served us so well," she said.
"Routine testing of border workers checks that those protective measures are working properly, it keeps our workers safe, assists us with detecting any cases so that we can contain them quickly, and ultimately helps to protect all New Zealanders from the virus."
Of the 18 workers who had been given fines, five were subjected to the 7-day test cycle and 13 were on the 14-day test cycle.
Covid-19 Response Minister Chris Hipkins recently announced all border workers who need to be regularly tested would, from mid-August, be able to have saliva PCR tests - instead of the invasive nasal swabs.
Ministry Chris Hipkins says border workers needing regularly testing can have saliva tests instead of nasopharyngeal testing from mid-August. Photo / Mark Mitchell
Such testing would be rolled out for those who need to be tested every week and progressively rolled out for the other workers over several months.
Hipkins said it was hoped this change would boost testing levels among MIQ staff.
There were no new cases of Covid-19 reported in the community today and five cases in MIQ in New Zealand.
Of the five people in MIQ with the virus, one had arrived from the UK, one from Brazil and three people had arrived from Fiji.
Another vessel in New Zealand waters is dealing with a Covid-19 outbreak.
Sixteen of the 18 crew members on the Spanish-flagged shipping vessel Playa Zahara have tested positive for the virus.
Crew members' swabs were taken in Port Taranaki after reports of a flu-like illness on board the ship.
After the tests were taken, the ship left the port for Lyttelton.
The ship had been at sea for three weeks prior to the reports of the illness and no one from New Zealand had been on board the vessel during that time, the ministry said.
Fifteen crew members onboard The Viking Bay fishing vessel have tested positive for Covid-19 and been moved to
a quarantine facility in Wellington. Photo / Mark Mitchel
The news of the Playa Zahara outbreak comes after another Spanish-flagged vessel, Viking Bay, also reported an outbreak of the virus among crew members.
All 15 of the infected crew members had been transferred to an on-shore quarantine facility in Wellington.
The ministry said the public health risk posed by both vessel outbreaks was low.
Investigations into the sources of these outbreaks and possible transmission was underway.
