Hitchcock was born in London in 1928, the only child of film Director Alfred Hitchcock and film Editor Alma Reville. The family moved to Los Angeles, California, in 1939. Once there, Hitchcock's father soon made his mark in Hollywood.

Patricia had a small uncredited role as an extra in her father's 1936 Sabotage. She and her mother, Alma Reville, are in the crowd waiting for, then watching, the Lord Mayor's Show parade.

As a child, Hitchcock knew she wanted to be an Actress. In the early 1940s, she began acting on the stage and doing summer stock. Her father helped her gain a role in the Broadway production of Solitaire (1942). She also played the title role in the Broadway play Violet (1944).

After graduating from Marymount High School in Los Angeles in 1947, she attended the Royal Academy of Dramatic Art in London and also appeared on the London stage.

In early 1949, her parents arrived in London to make Stage Fright, Hitchcock's first British-made feature film since emigrating to Hollywood. Pat did not know she would have a walk-on part in the film until her parents arrived. Because she bore a resemblance to the star, Jane Wyman, her father asked if she would mind also doubling for Wyman in the scenes that required "danger driving".

Hitchcock also worked for Jean Negulesco on The Mudlark (1950), which starred Irene Dunne and Alec Guinness, playing a palace maid, and she had a bit-part in DeMille's The Ten Commandments (1956).

She married Joseph E. O'Connell, Jr., 17 January 1952, at Our Lady Chapel in St. Patrick's Cathedral, New York. They decided to have their wedding there because Hitchcock had many friends on the East Coast and O'Connell had relatives in Boston. They had three daughters, Mary Alma Stone (born 17 April 1953), Teresa "Tere" Carrubba (born 2 July 1954), and Kathleen "Katie" Fiala (born 27 February 1959). Joe died in 1994. She currently lives in Solvang, California.

She also served as executive Producer of the documentary The Man on Lincoln's Nose (2000), which is about Robert F. Boyle and his contribution to films.

For several years, she was the family representative on the staff of Alfred Hitchcock's Mystery Magazine. She supplied family photos and wrote the foreword of the book Footsteps in the Fog: Alfred Hitchcock's San Francisco by Jeff Kraft and Aaron Leventhal, which was published in 2002. In 2003, she published Alma Hitchcock: The Woman Behind the Man, co-written with Laurent Bouzereau.

As well as appearing in ten episodes of her father's half-hour television programme, Alfred Hitchcock Presents, Hitchcock worked on a few others, including Playhouse 90, which was live, directed by John Frankenheimer. Acting for her father, however, remained the high point of her acting career, which she interrupted to bring up her children. (Hitchcock has a small joke with her first appearance on his show – after saying good night and exiting the screen, he sticks his head back into the picture and remarks: "I thought the little leading lady was rather good, didn't you?")