People arriving into the UK from Belgium, the Bahamas and Andorra will have to quarantine for 14 days.
Transport Secretary Grant Shapps said the changes start at 04:00 BST on Saturday except in Wales, where it started midnight on Thursday.
The Foreign Office is also warning against "all but essential travel" to the three countries, BBC reported
But travellers from Brunei and Malaysia arriving in England and Wales will no longer need to self-isolate, after a decrease in confirmed coronavirus cases.
People who do not self-isolate when required can be fined up to £1,000 in England, Wales, and Northern Ireland and those returning to Scotland could be fined £480, with fines up to £5,000 for persistent offenders.