Halting all flights in and out of the territory, the Northern Marianas will close its borders from Monday.
The Commonwealth Ports Authority said, however, that freight and medical transport would not be disrupted, including the daily mail service to Guam.
The announcement comes as the US territory became the latest in the Pacific to confirm an outbreak of Covid-19, with authorities so far confirming six cases and one death.
United Airlines has suspended its services from Saipan, as have most Asian airlines, which has led to the near total collapse of the Northern Marianas economy.
Star Marianas Air has also said it will suspend its inter-island flights from Friday, although cargo and medical evacuation flights between Saipan, Tinian and Rota would continue.