All Saudi citizens who did not have their second Covid-19 shot within the past three months must have a booster dose before travelling outside the country.
The rule will come into effect on Wednesday, February 9, the interior ministry said.
Children aged under 16 and people who fall into an exempt category on the Tawakkalna application do not need a booster to travel.
The Interior Ministry said that all passengers arriving to the kingdom, including residents and citizens, must show proof of having tested negative for the coronavirus within 48 hours of their departure to the country, even if they are fully vaccinated.
Children younger than 8 are exempt from this rule.
Face masks are mandatory in public spaces, including offices and malls.
The government has encouraged citizens and residents who have had both doses of a Covid-19 vaccine to come forward for a booster shot.
Anyone whose second dose was more than three months ago, or who has been recovered from Covid-19 for at least this period, is eligible for the supplementary shot.
Cases of the coronavirus in Saudi Arabia have declined in the past month.
On Thursday, the kingdom recorded four Covid-19 deaths and 3,852 new cases.
