The King and Queen, who are both in their 70s, have had three Covid vaccinations each and have mild symptoms.
They tested positive for Covid on Monday evening.
“The Royal couple have isolated themselves at home in accordance with the rules, and contact tracing is ongoing,” said the Royal Court in a statement on Tuesday afternoon.
The couple’s eldest daughter, Crown Princess Victoria, and her husband Prince Daniel had Covid in March last year.
Victoria’s brother, Prince Carl Philip, and his wife Princess Sofia, tested positive for Covid-19 in November 2020.