The Princess of Wales will make her first public appearance this year at Trooping the Colour.
Kate, who has been receiving treatment for an undisclosed form of cancer since late February, will ride in a carriage alongside her three children, Prince George, Princess Charlotte and Prince Louis.
Later, she is expected to join the King, her husband the Prince of Wales, and other royals on Buckingham Palace’s balcony for the fly-past.
The princess, 42, said: “I’m looking forward to attending the King’s Birthday Parade this weekend with my family and hope to join a few public engagements over the summer, but equally knowing I am not out of the woods yet.
“I am learning how to be patient, especially with uncertainty.
“Taking each day as it comes, listening to my body, and allowing myself to take this much needed time to heal.”
A Buckingham Palace spokesperson said on Friday: “His Majesty is delighted that the princess is able to attend tomorrow’s events, and is much looking forward to all elements of the day.”
Rishi Sunak and Sir Keir Starmer welcomed the news on social media, both describing Kate as an “inspiration” to those experiencing similar health issues.
This will be the princess’s first official outing of 2024 after she missed engagements at the start of the year when she was admitted to hospital for abdominal surgery on 16 January.
At the time her condition was thought to be non-cancerous, but tests after the successful operation found the disease, and Kate disclosed the diagnosis in March.
A time frame has not yet been set for Kate’s return to a full schedule of public engagements.