Sikorski was born in Zurich, but studied in Warsaw, first music at the Warsaw Conservatory and then philosophy at the University of Warsaw. He then studied in Lwów, which was Polish at the time, and Paris. In 1926, he became a teacher of composition at the Conservatory of Poznań. From 1927 to 1945, he taught at the Warsaw Conservatory. He was rector of the State Higher School of Music in Łódź. From 1951 to 1966, he taught music theory and composition at the Music Academy Warsaw. See: List of music students by teacher: R to S#Kazimierz Sikorski. During this time, he was president of the Polish Composers' Union.
He received many awards and honours, including: the National Music Award (1935), the Order of Polonia Restituta (1937), State Award first and second degree (1951, 1955, 1964, 1966), the Award of the Polish Composers’ Union (1951, 1975), the Gold Cross of Merit (1952), Commander's Cross of the Order of Polonia Restituta (1955), the Banner of Labour Order, First Class (1960), the Jurzykowski Foundation Award (1981). He died in Warsaw, aged 91.
Sikorski composed six symphonies, a symphonic allegro, two overtures (1945, 1954), some instrumental concertos, of which the clarinet concerto (1947) is the most important, a string sextet, three string quartets, choral and film music, including the music for the film Warsaw Premiere (Polish: Warszawska premiera), for which he won a State Award.
- Symphony No. 2 (1922)
- Stabat Mater, Oratorio for 4 Solo Voices, Mixed Choir and Orchestra (1948, 1950)
- Concerto for Flute and Orchestra (1957)
- Concerto for Trumpet, String Orchestra, 4 Kettledrums, Xylophone and Tam-tam (1960)
- Poliphonic Concerto for Bassoon and Orchestra (1965)
- Symphony No. 4 (1969)
- Four Polonaises of Versailles for Strings (after Manuscripts from the 18th and 19th c.) (1974)
- Warsaw Premiere (1951)
- "Kazimierz Sikorski" (in Polish). culture.pl. 2005. Retrieved 2008-12-05. CS1 maint: discouraged parameter (link)
- Wajszczuk, Błażej (28 June 2001). "Kazimierz Sikorski". Brief Biography. Polish Music Center. Retrieved 2008-12-05. CS1 maint: discouraged parameter (link)
- Marlewski, Adam (April 22, 2002). "Tomasz Sikorski". Andre Chaudron. Archived from the original on February 10, 2008. Retrieved 2008-12-05. CS1 maint: discouraged parameter (link)
- Jarocinski, Stefan. 1965. "Polish Music after World War II". The Musical Quarterly 51, no. 1 (January): 244–58.
- Thomas, Adrian. 2001. "Sikorski, Kazimierz". The New Grove Dictionary of Music and Musicians, edited by Stanley Sadie and John Tyrrell. London: Macmillan.
- Thomas, Adrian. 2005. Polish Music since Szymanowski. Cambridge & New York: Cambridge University Press. ISBN 0-521-58284-9