Ferguson died Sunday night at a clinic in Hampshire, England, after suffering a heart attack, a family spokeswoman said. He had been diagnosed as having prostate cancer in 1996 and had had several previous heart attacks.
The spokeswoman said the duchess, who recently spent time with her father, was on her way to Australia, where she had commitments as a spokeswoman for Weight Watchers, but would return to Britain at the end of the week. "She ... is grateful for the time she had with her father to say goodbye," she said.
Educated at Eton College and the Sandhurst military academy in England, Ferguson received a commission in the Household Cavalry, where he served for 19 years. For several years, he captained the Sovereign's Escort, mounted officers who escort Queen Elizabeth II during the Trooping the Color military parade held to mark her birthday.
A well-known figure in polo circles, Ferguson lost his job as manager of the elite Guards Polo Club in 1988 after a tabloid published photographs of him entering and leaving a seedy London massage parlor.
Further humiliation followed in 1994 with the publication of a memoir by polo-loving public relations executive Lesley Player, who claimed she had had an affair with Ferguson, forcing him to quit his role as sponsorship organizer at the exclusive Royal County of Berkshire Polo Club. He tried to ride out the scandal, but it was too much for Charles, and Ferguson was let go as the prince's polo manager after 21 years.
Ferguson stood by his fiery daughter as her marriage to the queen's second son, Prince Andrew, collapsed. A gruff character who was not afraid to speak his mind, he accused royal courtiers of undermining his daughter.
Sarah and an older sister, Jane, were children from his 1965 marriage to his first wife, Susan. The marriage broke up after Ferguson had an affair and his wife sought comfort with Argentine polo star Hector Barrantes. After the Fergusons divorced, she set up home with Barrantes on a ranch west of the capital, Buenos Aires.
Left to bring up his daughters alone, Ferguson married his second wife, also named Susan, in 1976. They had three children, Andrew, Alice and Eliza.
In addition to his daughter Sarah, he is survived by his wife and four children.