The monarch is experiencing “mild cold-like symptoms” but expects to continue “light duties” at Windsor over the coming week, the palace said.
“She will continue to receive medical attention and will follow all the appropriate guidelines,” it added in a statement.
The Queen, 95, had been in contact with her eldest son and heir, the Prince of Wales, who tested positive last week.
It is understood a number of people have tested positive at Windsor Castle, where the Queen resides.
Prime Minister Boris Johnson tweeted: “I’m sure I speak for everyone in wishing Her Majesty The Queen a swift recovery from Covid and a rapid return to vibrant good health.”
