"While not a threat to humans, it would devastate our national herd. Essentially, all animals that are of cloven hoof are at risk," Ardern told reporters in Wellington.
Ardern warned that the disease, first detected in Indonesia in April, has the potential to threaten up to 100,000 jobs in New Zealand's agriculture sector.
Foot and mouth disease is a severe, highly contagious viral disease of livestock.
It can have a significant economic impact, especially on a country like New Zealand which exported around 17 million sheep and two million cattle in the eight months up until May 2022.
A foot-and-mouth outbreak has ripped through two Indonesian provinces, killing thousands of cows and infecting hundreds of thousands more.
Ardern said New Zealand has never had an outbreak -- and wants to keep it that way by tightening border restrictions.
"We want to make sure that we've got all our settings in place to protect ourselves from this emerging threat," she added.
There are currently no direct flights from Indonesia to New Zealand, but Ardern said it is important to stop it from entering the country, potentially via Australian tourists who had visited south-east Asia.
Travellers from Indonesia will not be allowed to bring meat products into New Zealand, baggage will be screened and there will be disinfectant mats at airports to clean footwear.
In Australia, parcels and baggage from China and Indonesia are now being checked and there are also foot mats at airports in response to the disease.
Canberra has so far rejected opposition calls to close the border to Indonesia completely, but further measures have not been ruled out.
Ardern said her government is working with Australian authorities to try to further reduce the risk.
New Zealand is set to fully open its borders at midnight on Sunday to all visitors.
New Zealand's Biosecurity Minister Damien O'Connor said "vigilance is absolutely crucial" as the disease could also affect up to 77 percent of the country's wildlife population, including wild deer, pigs and sheep.
He referred to how foot and mouth devastated British farming in 2001 when millions of cattle and sheep had to be slaughtered.