UK tourists will no longer need to quarantine after holidaying in Portugal, but travellers returning from Croatia will now have to self-isolate.
Transport Secretary Grant Shapps said people will need to self-isolate for 14 days on return from Croatia, Austria and Trinidad and Tobago.
The changes apply to anyone arriving after 04:00 BST on Saturday.
Meanwhile, the Scottish government has added Switzerland to the lists of countries on its quarantine list.
It comes after thousands of British holidaymakers made a last-minute dash to get home from France last weekend, before quarantine measures came into force.
People who do not self-isolate when required can be fined up to £1,000 in England, Wales, and Northern Ireland. In Scotland the fine is £480, and up to £5,000 for persistent offenders.
The UK introduced the compulsory 14-day quarantine for arrivals from overseas in early June.
But the following month, the four UK nations unveiled lists of “travel corridors”, detailing countries that were exempt from the rule.
Since then it has periodically updated that list, adding and removing countries based on their coronavirus infection rates and how they compare with the UK’s.
The UK provides the largest number of overseas tourists to Portugal, with more than two million tourists visiting every year.
The Algarve coast is the most popular destination, with 1.2 million visitors from the UK last year.