Farrow was born in Los Angeles, California to John Farrow (an Australian film director) and the late Irish actress Maureen O'Sullivan. O'Sullivan and John Farrow were practicing Catholics, and Mia had a Catholic upbringing. Farrow was stricken with polio as a child and spent a year in an iron lung.

Farrow made her film debut in a 1947 short subject with her mother; the short was about famous mothers and their children modeling the latest fashions for families. In the 1950s, she appeared in the Cold War educational film, . She began her acting career by appear in supporting roles in several 1960s films. Her first leading role was in the 1968 horror film, , which was a critical and commercial success, establishing Farrow as a leading actress. Farrow became friends with director Roman Polanski and his wife Sharon Tate while filming "Baby".

Farrow was the person on the first issue of in 1974. Several of her subsequent films were disliked by critics (including 1972's "Follow Me!", which was given a harsh review by critic Roger Ebert [1]), but a number of her 1970s films were notable, including the 1971 thriller "See No Evil" and the 1974 version of , in which Farrow played "Daisy Buchanan". Farrow also appeared in a number of made for television films in the 1970s.

Farrow's relationship with director Woody Allen in the 1980s resulted in a number of film collaborations. Farrow appeared in most of Allen's critically acclaimed films during the decade and the early 1990s, including most notably (an Irish film) and the 1995 film, "Miami Rhapsody", which has been described by some critics as "Woody Allen"-esque [2]. Farrow appeared in many lower-budget and television films throughout the late 1990s and early 2000s. She has been cast in the role of "Mrs. Baylock", the Satanic nanny, in the 2006 remake of the horror film,

Farrow married singer Frank Sinatra on July 19, 1966, when she was 21 and he was 50. While she was filming with director Roman Polanski, Sinatra served her divorce papers in front of the cast and crew. The move came as a shock to Farrow, who did not think that Sinatra would divorce her because she had refused his prior demand that she quit filming in order to work on his movie, and widely outgrossed it at the box office, Farrow asked producer Robert Evans to run an ad touting the fact as a way of getting back at Sinatra. Evans obliged her.

Farrow married Hungarian Jewish pianist André Previn in 1970. His former wife, songwriter Dory Previn, blamed Farrow for his leaving her and wrote a scathing attack in a song entitled "Beware of Young Girls". Farrow and Previn had three biological children (twins Matthew and Sascha, born in 1970; and Fletcher, born in 1974) together and adopted three children from Korea, Soon-Yi, Lark Song, and Daisy. André and Mia divorced in 1979, but remained on good terms. Fletcher Previn appears one of Farrow's film collaborations with Woody Allen,

In the 1980s and early 1990s, Farrow spent many years with but did not marry nor live with director Woody Allen. The two had a son, Satchel (born in 1987, who is now called Seamus Farrow, and is well-known as a child prodigy). They also adopted a son and daughter together. They separated after Allen began a relationship with Farrow's adopted daughter Soon-Yi, whom he later married. During the custody battle Farrow filed child abuse charges against Allen, involving her other daughter, Dylan.

Farrow continued to adopt children as a sole parent. She is active in agencies that encourage adoption and is a UNICEF Special Representative. By 1994, Farrow had 14 children, 9 of them adopted: 6 from her marriage with André Previn (3 adopted) and 3 from her time with Woody Allen (2 adopted). Farrow is estranged from Soon-Yi Previn since her marriage to Woody Allen. Farrow's adopted daughter, Tam Farrow, died in March 2000 at age 19, after a long illness.