Hoffmann was born in Prague-Smíchov, as the ninth child of weaver Karel Hoffmann. He was a weak child, and one of his older brothers chose for him to learn the violin as a "lighter work".[1] In 1885, he began his studies at the Prague Conservatory, as a pupil in the class of Antonín Bennewitz. The first important event of his career was his entry to the chamber music class of Hanuš Wihan.[1] There he met Josef Suk, Oskar Nedbal, and Otto Berger – his future colleagues and collaborators from the Bohemian Quartet. They founded the quartet officially in 1892, and the activity of the ensemble lasted 42 years. Hoffmann was the only permanent member of the ensemble throughout its 1892–1934 existence.[2] In 1934, after the death of violist Jiří Herold, Hoffmann founded the Bohemian Trio with Ladislav Zelenka and Jan Heřman.[2]
In 1932, he developed cancer and was forced to undergo surgery. He recovered for a short time and resumed his activities. However, a second surgery in 1934 was unsuccessful and Karel Hoffmann passed away in 1936.[2]
Benešová, Eva (July 2009). "200 let pražské konzervatoře. VII. Karel Hoffmann a Vilém Kurz (200 Years of the Prague Conservatory. VII. Karel Hoffmann and Vilém Kurz)". Hudební rozhledy (in Czech). 7: 50–51.
Černušák, Gracián; Štědroň, Bohumír; Nováček, Zdenko, eds. (1963). Československý hudební slovník I. A-L (in Czech). Prague: Státní hudební vydavatelství. pp. 450–451.