Health Secretary Sajid Javid, who replaced Matt Hancock in the role last month, got the positive result from a lateral flow test that he took after feeling "a bit groggy" and says he is now self-isolating at home with his family.
Mr Javid's symptoms emerged just three days after he visited a care home in Streatham, south London.
He was there on Tuesday, having earlier been in parliament. He returned to the Commons on Wednesday and spoke about the Health and Care Bill in the afternoon.
Photo agency Politics Pics has taken pictures of Mr Javid leaving Number 10 Downing Street on Friday at around 10.15am after allegedly meeting with Prime Minister Boris Johnson.