Visitors to six Greek islands, mainland Portugal, Gibraltar and French Polynesia will have to quarantine for two weeks when they return to Wales.
The Welsh Government is bringing in the new rules from Friday morning in the first time it has brought in different quarantine rules from England.
The new rules will apply to people returning to Wales regardless of whether they land at Cardiff or any other airport in the UK.
None of the changes will apply to people who are returning to England.
In a statement on Thursday, health minister Vaughan Gething said it comes as a result after "a large number of cases of coronavirus have been imported into Wales from tourists", especially from the Greek islands.
Mr Gething said people returning from the following countries and islands will have to self-isolate for 14 days, with effect from 4am on September 4:
Portugal (The Azores and Madeira remain exempt)
Gibraltar
French Polynesia
Passengers returning from these Greek islands will also have to self-isolate for 14 days from 4am on September 4:
Mykonos
Zakynthos
Lesvos
Paros
Antiparos
Crete
Mr Gething said: "This action is being taken as a result of a large number of cases of coronavirus have been imported into Wales from tourists returning from the Greek islands, in particular. In the last week, there have been more than 20 cases confirmed in passengers on one flight from Zante to Cardiff."
In just one week, NHS Wales' Test, Trace, Protect service said it had identified six clusters of the virus in Wales, amounting to over 30 cases linked to the island of Zante.
Mr Gething said there was "clear advice from the Joint Biosecurity Centre (JBC) report that travel from the following countries and territories constitutes a public health risk".
It follows a meeting today of all the devolved administrations at which Mr Gething had previously said he would be pushing for changes to the quarantine rules.
However England has decided not to bring in any changes to its rules for either Greece or Portugal.
Transport Secretary Grant Shapps tweeted: “We continue to keep the Travel Corridor list under constant review & won’t hesitate to remove countries if needed. However, there are no English additions or removals today."
Scotland had already brought in a two-week quarantine for anyone returning from Greece, which came into force on Thursday morning.
The Covid cases from Zante that arrived in Wales were from travellers on four different flights, two of which landed in England.
Mr Gething said public health teams are concerned current control measures for returning travellers are "insufficient" and have called for a meeting with the UK Government and devolved nations.
