The cellist Clemens Hagen comes from a Salzburg musical family and received his first instrumental lessons at the age of six. Two years later, he began his studies at the University of Mozarteum; he later transferred to the Basel Music Academy. His teachers included Wilfried Tachezi and Heinrich Schiff. In addition to numerous first prizes, in 1983 Clemens Hagen received the Special Prize from the Vienna Philharmonic and the Karl Böhm Prize.
As a soloist, Clemens Hagen has performed with internationally renowned orchestras such as the Berlin and Vienna Philharmonic, the Vienna Symphony, the Concertgebouworkest Amsterdam, the Camerata Salzburg, the Deutsche Kammerphilharmonie Bremen, the Chamber Orchestra of Europe, the SWR Symphony Orchestra, the Cleveland Orchestra, and the NHK Symphony Orchestra Tokyo. He has worked under conductors such as Nikolaus Harnoncourt, Claudio Abbado, Franz Welser-Möst, Ingo Metzmacher, Sándor Végh, Daniel Harding, Zoltán Kocsis, and Sylvain Cambreling.
Clemens Hagen considers chamber music an essential complement to his solo work: foremost among these is the Hagen Quartet, with which he has been performing worldwide for 40 years and has recorded more than 45 CDs for Deutsche Grammophon. Other chamber music partners include Gidon Kremer, Renaud Capuçon, Leonidas Kavakos, Maxim Vengerov, Christian Tetzlaff, Yuja Wang, Evgeny Kissin, Mitsuko Uchida, Martha Argerich, Hélène Grimaud, Kirill Gerstein, Stefan Vladar, Leif Ove Andsnes, and Sabine Meyer.
In 2003, Claudio Abbado invited Clemens Hagen to join his newly founded Lucerne Festival Orchestra, of which he is still a member. Since the 2018/19 season, he has been the cellist of the Vienna Piano Trio. He has been teaching cello and chamber music at the University of Mozarteum since 1988, and since 2003 he has held a professorship there.
Clemens Hagen plays a cello by Antonio Stradivari from 1698.