The Labour leader has said he does not have any symptoms and will be working from home until next Monday.
He said in a tweet: “This morning I was notified that I must self isolate after coming into contact with someone who has tested positive for Covid-19.
“I have no symptoms and will be working from home until next Monday.”
It is not yet clear whether Starmer will take part in prime minister’s questions in the Commons virtually on Wednesday.
If not, deputy leader Angela Rayner may face Boris Johnson in his place.
It is the third time Starmer has had to self-isolate since the start of the pandemic last year.
In mid-September, his daughter tested positive for the disease.
Most recently, he had to self-isolate in December after a staff member tested positive for the virus.
Starmer has previously tested negative for the virus.