All passengers coming into Ireland will need to show proof of a negative or not-detected COVID-19 test from Sunday December 5th.
It follows a delay of the regulations, which were meant to be in place from Friday.
Justice Minister Helen McEntee earlier said there had been a "slight delay" in the signing off of the regulations.
However Health Minister Stephen Donnelly has now signed the regulations, amending requirements around international travel.
This follows a Government decision on Tuesday to respond to the emergence of the new Omicron COVID-19 variant.
A passenger with proof of vaccination or recovery can show either a negative PCR test result taken within 72 hours of arrival - or a negative antigen test result taken within 48 hours of arrival.
However, only Rapid Antigen Tests listed on the common EU Rapid Antigen Test list will be accepted - and it must be carried out by a health professional or skilled testing personnel.
Passengers without proof of vaccination or recovery must show a negative PCR test result taken within 72 hours of arrival.
And those who arrive without a negative test result are required to home quarantine and take a PCR test within 36 hours of arrival.
A subsequent negative/not detected text will mean a passenger can exit home quarantine.
But if no PCR test is taken, then the passenger must remain in home quarantine for 10 days after arrival.
These new measures are intended to be temporary and will be kept "under constant review", the Minister says.