The changes come amid increased concern over the newly discovered Omicron variant of Covid-19.
Prior to Wednesday (1 December), travellers from the UK were able to enter Spain with a vaccination certificate or a negative Covid-19 test.
The changes will mean that from Wednesday (1 December), all travellers from the UK will need to show proof of being fully vaccinated, with both doses of a two-dose vaccine or one dose of a one-dose vaccine, at least 14 days prior to arrival.
Children under 12 years old are exempt when travelling with an adult.
All passengers must also present a QR code which is obtained from filling in a health control form available via Spain Travel Health.
The new legislation is for UK travellers prior to their arrival to the whole of Spain, including the Balearic Islands and the Canary Islands.
The Spanish Tourism Board said: "Spain reinforces its position as a safe holiday destination with one of the highest vaccinations rates worldwide (almost 90% of the population age 12 and over) and one of the lowest Covid rates in Europe.
"Based on Spain’s Ministry of Health data from a seven-day period up until 26 November 2021, the accumulated incidence rate of Covid infection in Spain is 97.98 per 100,000 residents."
The UK Foreign Office has updated its advice to reflect the new rules.
It said: "All passengers (including children under 12 years old) travelling by air or sea must complete and sign an online health control form no more than 48 hours prior to travel.
"Spain will accept the UK’s Covid-19 vaccination record. If you are travelling with a printed PDF proof of vaccination status, it must date from 1 November to ensure that the certificate can be scanned successfully."
