The decision affects parties that would traditionally be held at Buckingham Palace and the Palace of Holyroodhouse in Edinburgh, according to HELLO! UK.
The royal garden parties are typically one of the big highlights on Her Majesty's summer calendar, and this marks the second year the large-scale events will not be held.
The U.K. has seen COVID-19 cases skyrocket since late 2020 due to a new coronavirus strain. Discovered in September, it is believed to be between 50 and 70 per cent more transmissible, scientists say.
When 2020's garden parties were cancelled, guests invited to three garden parties at Buckingham Palace that year would be asked to 2021's parties instead. The latest news obviously changes this.
The Queen usually welcomes more than 30,000 guests to enjoy a lovely summer afternoon in the beautiful gardens of Buckingham Palace or the Palace of Holyroodhouse. The intention is for the monarch to speak to a broad range of people from all walks of life who have had a positive impact on their communities.
The Queen and Prince Philip are isolating at Windsor Castle, where they spent much of 2020. Royals fans last saw Her Majesty deliver her annual Christmas speech, in which the 94-year-old discussed the coronavirus' impact, and encouraged viewers to remember hope and good deeds.
"We continue to be inspired by the kindness of strangers, and draw comfort that even on the darkest nights, there is hope in the new dawn," she said in the moving address.
There have been more than 85.8 million cases of COVID-19 confirmed in 191 countries and regions with more than 2.7 million of those cases in the U.K., according to the Johns Hopkins University School of Medicine.