Tuomas Haapanen studied violin at the Sibelius-Academy during 1938-42 and 1945-48 (Gösta Schatelowitz and Eric Cronvall), where he achieved his diploma 1948. Between the years 1949- 1962 he continued his violin studies periodically in Paris (Léon Nauwinck and René Benedetti).
During the years 1952-1962 he worked as violinist in the Finnish Radio Symphony Orchestra, from 1958 as Leader. Between the years 1950 and 1980 (appr.) he was very active in performing as orchestra soloist, with his own recitals and in many different chamber music ensembles. In 1962, when a new Music Institute (later Conservatory) was founded in Turku, Tuomas Haapanen was invited to take the post of main violin teacher there. After sixteen years of successful teaching in Turku, he was chosen professor of violin at the Sibelius Academy. During the years 1988-1990 he also served as principal of the Sibelius-Academy.