Downing Street says Deputy Prime Minister Dominic Raab would have made any urgent decisions in his place.
Boris Johnson had a “minor routine operation related to his sinuses” under general anaesthetic at a London hospital on Monday morning, No 10 has said.
The prime minister had the operation on Monday morning and was back in Downing Street at 10:00 BST.
A Downing Street spokesman said Deputy Prime Minister Dominic Raab would have made any urgent decisions in his place.
They added that the PM’s return to work would depend on how he was feeling.
However, he is expected to chair a meeting of his senior ministers on Tuesday morning.