The Health Minister says everyone coming into the country must self-isolate, with no exceptions.
It comes following reports on social media of tourists entering the country and not staying in quarantine for two weeks.
It is mandatory for people to fill in a self-locator form at airports letting officials know where they plan to stay for 14 days.
Health Minister Stephen Donnelly says people coming into the country should know what's expected:
A tour operator in Co. Clare cancelled a guided cycle for two US tourists last night, after they said they hadn't isolated for two weeks.
The visitors said they filled in the self-locator form but didn't think the quarantine period was necessary.
Janet Kavanagh, owner of E-Whizz, says she didn't feel comfortable allowing them to follow through on the booking: