Kenji Kobayashi was born in 1933 in Tokyo, Japan. He studied violin with Shinichi Suzuki, Zenzo Matsumoto, Akeo Watanabe. He appeared as the soloist of Tokyo Philharmonic Orchestra in 1950. In 1952 he entered Juilliard School of Music in New York and studied with Louis Persinger and then with Ivan Galamian. He was a soloist with Juilliard Orchestra in 1958 and made Town Hall debut recital in 1961 with a highly critical appraisal. In the same year he was invited by Szymon Goldberg and made recitals in Concergebouw in Amsterdam and at Darmstadt Festival in Germany.

In 1966 and 1967 he participated Marlboro Music Festival in the United States. He presides the New Arts String Quartet since 1975 and made concerts tours to Europe, Asia and Australia. From 1972 to 1990 he was the concertmaster of the Tokyo Metropolitan Symphony Orchestra.

He is professor of violin at Toho Gakuen School of Music and Tokyo University of Art and Music. He was a jury member at the Paganini Violin Competition in 1993 and 2001, at the International Violin Competition "Rodolfo Lipizer" (Italy) in 2001, at the International Violin Competition "Sion-Valais" (Switzerland) in 2002 and at the Young Artist Competition in Novosibirsk (Russia).