Travellers from mainland Portugal to England will have to quarantine from 04:00 BST on Saturday, just a few weeks after the country was put on the safe travel list.
Wales and Scotland had already imposed the mandatory two weeks of self-isolation earlier this month.
Quarantine-free travel is still allowed from the Portuguese islands, the Azores and Madeira.
Meanwhile, Sweden has been added to the list of countries exempt from quarantine requirements. Transport Secretary Grant Shapps said that because of "enhanced data" the government was able to assess the infection rates of islands separate to their mainland countries.
He also stressed that travellers must fill out the Passenger Locator Form on arrival to the UK, a day after the prime minister said enforcement of this part of the quarantine rules would be stepped up.
"It is a criminal offence not to complete the form and spot checks will be taking place," Mr Shapps said.
People travelling to England and Wales from Hungary, French Polynesia and Reunion will also be required to self-isolate, announced the UK government this Thursday.
