Hazel Dorothy Scott was born on June 11, 1920, in Port of Spain, Trinidad and Tobago, the only child of R. Thomas Scott, a West African scholar from Liverpool, England, and Alma Long Scott, a classically trained pianist and music teacher. In 1924 she and her mother moved to Harlem in New York City, where they lived with her grandmother. She could play on the piano anything she heard, and her mother's training turned her into a child prodigy. At eight she began studying with Oscar Wagner of the Juilliard School and received scholarships there. In 1933 her mother put together Alma Long Scott's All-Girl Jazz Band, in which Scott played piano and trumpet.

By sixteen she was a regular on Mutual Broadcasting System radio programs, where she earned the nickname "the hot classicist," and in the mid-1930s she played the Roseland Dance Hall with the Count Basie Orchestra. Her New York stage credits included the Cotton Club Revue of 1938, Sing Out the News (1938), and The Priorities of 1942. From 1939 to 1943 she was a leading attraction at both the downtown and uptown branches of Café Society, the racially integrated Greenwich Village club run by Barney Josephson, where she took the headline spot after Billie Holiday left. There she built an act around swinging classical pieces. Her first solo album for Decca, Swinging the Classics, was recorded on December 11, 1940, and released in 1941, and Café Society's From Bach to Boogie-Woogie concerts took her to Carnegie Hall in 1941 and 1943.

Scott appeared as herself in five Hollywood films: The Heat's On, I Dood It, and Something to Shout About (all 1943), Broadway Rhythm (1944, alongside Lena Horne), and Rhapsody in Blue (1945). She refused the maid and "singing servant" parts she was first offered, insisted on the credit "Miss Hazel Scott as Herself," and wore her own clothes and jewelry on screen. In 1945 she married the minister and congressman Adam Clayton Powell Jr.; their son, Adam Clayton Powell III, was born the following year. In 1950 she became the first Black American to host her own television series when The Hazel Scott Show premiered on the DuMont network; the band behind her on the program included Charles Mingus and Max Roach.

She had long refused to play segregated venues, and in 1949 she won a lawsuit against a restaurant in Pasco, Washington, that would not serve her. In June 1950 her name appeared in Red Channels, and on September 22, 1950, she appeared voluntarily before the House Un-American Activities Committee, denying any knowing connection to the Communist Party. Her television show was cancelled a week later, on September 29. She suffered a nervous breakdown in 1951 and kept working in the United States and Europe. In January 1955 she recorded Relaxed Piano Moods as a trio with Mingus and Roach for their Debut label, the album most often singled out as her finest jazz record. After separating from Powell (they divorced in 1960), she moved to Paris in 1957 and worked in Europe for a decade. She appeared in the French crime film Le désordre et la nuit (1958), recorded several EPs for Polydor, and in 1963 marched with James Baldwin and other American expatriates to the US Embassy in Paris in support of the March on Washington.

Scott returned to the United States in 1967. She played nightclubs and appeared on daytime television, including a 1970 episode of The Bold Ones: The New Doctors and a 1973 wedding-song scene on the soap opera One Life to Live. Through her longtime friend Dizzy Gillespie she joined the Bahá’í Faith in 1968, and in 1971 she co-presented a musical program with him at a Bahá’í conference in Kingston, Jamaica. Her late recordings include the 1979 LP Always on Image Records. She passed away of cancer at Mount Sinai Hospital in Manhattan on October 2, 1981, at age 61, and was buried at Flushing Cemetery in Queens, near Louis Armstrong, Johnny Hodges, and Gillespie. Her life has drawn renewed attention since: Dance Theatre of Harlem staged a ballet about her in 2022, and the PBS American Masters documentary The Disappearance of Miss Scott aired on February 21, 2025.

Scott's signature was the fusion that gave her first Decca album its title: she took Bach, Liszt, Chopin, Rachmaninoff, and Scarlatti pieces and swung them, and on her own tunes such as "Hazel's Boogie Woogie" and "A Rainy Night in G" she moved easily between classical and jazz idioms. AllMusic's Ron Wynn calls her a good bebop soloist, a nice ballad interpreter, a fair blues player, and an underrated vocalist, and notes that some critics found the classical numbers gimmicky and that her nightclub act often worked better than her studio albums. Her training came from her mother and from a Juilliard professor, and she was already playing Café Society while still in school. In the small-group setting of Relaxed Piano Moods, with Charles Mingus on bass and Max Roach on drums, she plays standards such as "Like Someone in Love" and "A Foggy Day," her own "Peace of Mind" and "Git Up From There," and the Duke Ellington and Johnny Hodges number "The Jeep Is Jumpin'," with no classical material on the program. AllMusic lists Art Tatum, Earl Hines, and Bud Powell among her related artists, and Alicia Keys named her as an inspiration for the two-piano performance she gave at the 2019 Grammy Awards. Her public stands against segregation, in clubs, in court, and in the film studios, are as much a part of her reputation as the playing.