Franz Reizenstein's parents were Dr. Albert Reizenstein (1871–1925) and Lina Kohn (b. 1880), both of Nuremberg, Germany. The family was Jewish and counted many professionals, scientists, bankers, and musically inclined people among its members.
Reizenstein grew up in Nuremberg and was considered a child prodigy. He composed his first pieces when he was 5, and by the age of 17 he had written a string quartet. His well-to-do and artistic family encouraged him to play chamber music at home. Eventually he was sent to study under Paul Hindemith at the Berliner Hochschule für Musik.
In 1934 he emigrated to England at the age of 23 to escape the Nazis, one of nearly 70 Jewish composers to do so from 1933–1945. Once in England, he furthered his studies under Ralph Vaughan Williams at the Royal College of Music, and began to incorporate English music into his works. He also studied the piano for eleven years with Solomon Cutner. He eventually became a professor at the Royal Academy of Music and the Royal Northern College of Music (then the Royal Manchester College of Music) in Manchester. Amongst his pupils at the Royal Academy of Music was Philip Martin whom he taught piano and composition. His compositional posts were extended when he was invited for six months as a Visiting Professor of Composition at Boston University in the United States, where there were also special concerts given of his works.
Reizenstein published his first piece, the Suite for Piano, Op. 6, in 1936. He gained more attention with the "virtuosic and flamboyant" Prologue, Variations and Finale, Op. 12, composed for the violinist Max Rostal. It was inspired by an extended tour which he took to South America (undertaken with another legendary violinist, Roman Totenberg). Reizenstein performed as a pianist as well as working as a composer.
At the start of World War II, Reizenstein, as a German, was interned in Central Camp in Douglas, Isle of Man. He continued to compose while within the camp although he was soon released, along with the other internees who did not pose a threat to the British.
He composed several chamber and piano works, which are highly regarded, as well as a number of orchestral works, overtures and concertos (a Concerto for String Orchestra, two Piano Concertos, a Violin Concerto and a Cello Concerto). Reizenstein is best remembered for his Piano Quintet in D major, Op. 23 (1949), of which the critic Lionel Salter wrote in Gramophone in July 1975: It "stands alongside Shostakovitch's as the most noteworthy of this century's piano quintets."
He also wrote two operas, Men Against the Sea (1949) and Anna Kraus (1952), and composed lavish orchestral scores for the Hammer horror film The Mummy (1959) and the cult British horror film Circus of Horrors (1960).
Reizenstein contributed the Concerto Popolare ("A Piano concerto to end all piano concertos") to Gerard Hoffnung's first music festival in 1956. Hoffnung's festivals were comedy events, trading on the musical knowledge of the audience. The premise of the Concerto Popolare is that the orchestra believes it is playing Tchaikovsky's First Piano Concerto, but the pianist believes he or she is playing the Grieg Piano Concerto. A pitched musical battle ensues, dragging in other themes (notably from Rhapsody in Blue, the Warsaw Concerto and the music-hall song "Roll Out the Barrel"). The soloist at the premiere was Yvonne Arnaud (otherwise a renowned actress), who had been chosen after Hoffnung's first choice, Eileen Joyce, declined.
Also popular was his set of Variations on The Lambeth Walk (a popular song of the 1930s), for solo piano, each variation being a parody of the style of a major classical composer. The composers parodied are Chopin, Verdi, Beethoven, Mozart, Schubert, Wagner and Liszt.
He married in England, and he and his wife had a son.
Through his mother's Kohn family, Reizenstein was related to the writer Catherine Yronwode.