Her father, Donald Cole, was a consulting engineer, and died in 1926 when Kim was only 3 years old. Her mother, Grace Lind, once performed as a concert pianist. She had one brother who was eight years older than she, and she was educated at Miami Beach High.
According to an in-depth article on Kim Hunter by Joseph Collura in the October 2009 issue of "Classic Images", Kim was quiet and painfully shy as a child and overcame it through the guidance of a local dramatics teacher, a Mrs. Carmine. Included were diction, voice and posture lessons.
She studied at the Actors Studio and her first professional appearance was as "Penny" in "Penny Wise" in Miami in November 1939. Then, she joined a repertory group called "Theatre of Fifteen", but it disbanded in 1942 when WWII took away most of its male members.
She made her Broadway debut performance as "Stella" in "A Streetcar Named Desire" at the Ethel Barrymore Theatre, New York, in December 1947 that was the 1947-1948 season's success and for which she won the Critics Circle and Donaldson awards.
A one-time student of the Pasadena Playhouse, she was appearing in the 1942 production of "Arsenic and Old Lace" when she was discovered by an RKO talent hunter who signed her to a seven-year contract for David O. Selznick's company. Selznick suggested she change her first name to "Kim" and a RKO secretary suggested the last name of "Hunter". A few years later, Irene Mayer Selznick, David's ex-wife by then, recommended Kim for her reprise role of "Stella" in A Streetcar Named Desire (1951), for which she won an Oscar.