Reuters reports Charles will be crowned in a ceremony that dates back 1000 years, surrounded by foreign heads of state and dignitaries. But the participation of his younger son had been in doubt after the 38-year-old heavily criticised his family in a book and documentary series.
Buckingham Palace and a spokesperson for the couple confirmed that Harry, known as the Duke of Sussex, would attend the 6 May event while Meghan would remain in California with the couple's two young children.
Their eldest, Archie, turns four on the same day.
"Buckingham Palace is pleased to confirm that the Duke of Sussex will attend the Coronation service at Westminster Abbey," the palace spokesperson said.
"The Duchess of Sussex will remain in California with Prince Archie and Princess Lilibet."
Harry and Meghan stepped down from royal duties in 2020 and moved to California, saying they wanted to forge a new, independent life, free of the scrutiny of the British press.
They agreed with the royal family that they would not take part in any future official royal events or tours, and they have only been seen in Britain on a handful of occasions since they left, including for the funeral of Queen Elizabeth, who died after a 70-year reign.
Tensions soon emerged following their departure and in recent months Harry has published a memoir containing intimate revelations about the British royal family while the couple also appeared in a Netflix documentary series.
Among their many accusations, they said some royals, including stepmother Camilla and brother William - the heir to the throne - had leaked stories to tabloid newspapers to protect themselves or enhance their reputations.
They also said the royal family had dismissed the race-related hounding of Meghan by the press as a rite of passage and compared her treatment to the intense media intrusion that his mother Princess Diana had suffered before her death.
Some media reports had suggested that Harry wanted an apology from his family before he agreed to attend the coronation - an event that will be marked in Britain by a public holiday.
Asked in one interview in January whether he would attend, Harry said: "There's a lot that can happen between now and then. But the door is always open."
Buckingham Palace had made clear that Harry - one of the most popular members of the royal family before he left the country - had been invited to the event.
Harry was last in Britain in late March, attending a court case he and other high-profile figures have brought against the publisher of the Daily Mail newspaper over allegations of phone-tapping and other privacy breaches.
The publisher denies the accusations. The case is one of several that the prince has brought against British newspapers.
Prince Harry and Meghan in London in June 2022 during Queen Elizabeth II's platinum jubilee celebrations. File photo. Photo: AFP