Sarah comes from aristocracy with royal Stuart ancestry. On her father's side, Sarah is a descendant of King Charles II of England from two of his illegitimate sons Charles Lennox, 1st Duke of Richmond and James Scott, 1st Duke of Monmouth. She is a great-great-granddaughter of William Montagu-Douglas-Scott, 6th Duke of Buccleuch and a great-granddaughter of Mervyn Wingfield, 8th Viscount Powerscourt. Her grandmother was Lady Marian Louisa Montagu-Douglas-Scott a first cousin of Lady Alice Christabel Montagu-Douglas-Scott, who became after her marriage with Prince Henry, Duke of Gloucester, Princess Alice, Duchess of Gloucester, an aunt of Queen Elizabeth II.

Sarah and Prince Andrew's romance began after some scheming to bring them together was orchestrated by Diana, Princess of Wales in 1985. Early in 1986 the couple were engaged and subsequently married in Westminster Abbey on 23 July 1986. Prince Andrew had the title of The Duke of York bestowed upon him by the Queen. Sarah automatically became Her Royal Highness The Duchess of York. In 1987, the Duchess became the first lady in the Royal Family to receive her Private Pilot's License.

By 1992, the marriage was experiencing trouble and the couple had drifted apart. After some 4 years of being officially separated, the Duke and Duchess made the mutual decision to divorce in 1996. The Duke and Duchess of York remain close friends and share in the upbringing of their two daughters.

After her divorce the press criticism was constant, focusing not only on her weight (tabloid headline writers tagged her 'the Duchess of Pork') but also on her lifestyle and perceived extravagance. Having forgone a large divorce settlement in the hope of maintaining a civil relationship with the royal family, the Duchess set out in 1996 to establish a commercial and media career in the United States. She felt strongly that she should not work commercially in Britain and opted to commute regularly between her home outside London and paid commitments in the US. Having lost weight and discovered new confidence, Sarah felt able to pass on her experience to others as the U.S. spokesperson for Weight Watchers International. The Duchess also brought attention to child obesity and called for efforts to address this problem.

Sarah’s other commercial interests have included Wedgwood china, home fragrances for U.S. retailer Bath & Body Works, and a signature line of Moissanite jewelry for K&G. Sarah is also a sought-after public speaker represented by the prestigious Washington Speakers Bureau. Over the course of several years, these activities, as well as the success of her many books, allowed Sarah to overcome the multi-million pound debts she amassed in the 80s and 90s.