Charles inherited Birkhall from his grandmother when she died in 2002, and often spends summers there with his wife the Duchess of Cornwall.
Clarence House confirmed the diagnosis, saying despite the symptoms the future king "otherwise remains in good health".
As reported by BBC, the statement also said that the 72-year-old Duchess has also been tested for COVID-19 and her results are negative.More news: Morris County Jail Inmates To Be Released
The official statement stated that the tests conducted for both of them were conducted by the NHS in Aberdeenshire.
The shock diagnosis comes after Queen Elizabeth II fled to Windsor Castle to self isolate. For the latest on COVID-19, readers are encouraged to use online resources from CDC, WHO, and local public health departments and visit our coronavirus hub.
Charles met Prince Albert of Monaco, who later tested positive, at a charity event in London on March 10.
Medical advice is that it's unlikely to escalate into a more serious case.More news: Karl-Anthony Towns: Mother in coma after showing COVID-19 symptoms
Britain's Press Association, citing a source, said the prince and the duchess remained in good spirits, and that Charles was not bedridden.
Royal commentator Dickie Arbiter has stated that Buckingham Palace reports Her Majesty "remains in good health". This has caused a stir in the entire royal family. Meanwhile, Meghan Markle and Prince Harry are now in Canada with their son Archie.
The prince also attended a Mansion House dinner on the 12th and held multiple private meetings since working from home.More news: Gunmen storm Sikh religious complex in Kabul