The 95-year-old monarch, who is double jabbed, will remain at her beloved sanctuary in Aberdeenshire as planned.
The employee was sent home on Saturday following a PCR test.
A Buckingham Palace spokesman said: “We have procedures in place should a member of any team get Covid.”
It is the Queen’s first stay Balmoral since the death of her husband the Duke of Edinburgh in April.
She has been joined by family members including the Duke of York and his ex-wife Sarah, Duchess of York.
The Duke and Duchess of Cambridge and their children are expected to arrive later this month.
Scotland has been a welcome retreat for the royal family since Queen Victoria’s day, with the Windsors relaxing and enjoying country pursuits in the stunning setting of the Scottish Highlands.