David Cassidy was born on April 12, 1950 in Manhattan, to Jack Cassidy, a very skilled actor and singer, and Evelyn Ward, an actress. By the time he was five, his parents were divorced and Jack had married actress Shirley Jones, an actress who in 1955 had just made Oklahoma! (1955). When David was about 10, his mother moved to California from New Jersey. A few years later, she married a director and, like Jack Cassidy and Shirley Jones, the marriage ended in divorce. David was thrown out of schools and hardly made it through one year of college. When he was eighteen, he went east to New York to perform in a play called "The Fig Leafs are Falling." He did some other spots on TV, but in 1970 he got the opportunity to play Keith Partridge on the TV show The Partridge Family (1970). (He did not know until he got the part that his real life stepmother Shirley Jones was to play his mother Shirley.) The show ended in 1974, but not the close relationship he had with his "sister" Susan Dey, who played Laurie Partridge. In 1976, David's father Jack died when his apartment caught on fire. That year, David married Kay Lenz, but they later divorced. He married again to a horse trainer in 1984, but it did not last either. In 1990, he married Sue Shifrin. He had two children, a son named Beau, with Sue, and actress Katie Cassidy. In 1994, he wrote a book about his years being Keith Partridge, and performed updated songs from the Partridge Family years.

David died on November 21, 2017, in Fort Lauderdale, Florida. He was sixty seven.