Scots returning from Portugal and French Polynesia will have to self-isolate for 14 days after the two countries were added to the quarantine list.
The measures came into effect from 4am on Saturday.
The Scottish Government said the risk of importation of coronavirus into Scotland by people who have visited Portugal “is too high to ignore”.
Portugal and French Polynesia are the latest countries to join the growing list of nations moved from the exempt to the quarantine list amid rising coronavirus cases in Europe and around the world.
Failure to comply with requirement to quarantine can result in a fine of £480.
On Thursday, Justice Secretary Humza Yousaf said:“We are in the midst of a global pandemic and the situation in many countries can change suddenly.
“The requirement for travellers to quarantine for 14 days on arrival from a non-exempt country is vital to help prevent transmission of the virus and to suppress it – not doing so poses a significant risk to wider public health across Scotland.
“Therefore, people should think very hard before committing to non-essential travel abroad.”