Kaufmann was born in Munich. His father worked for an insurance company, and his mother was a kindergarten teacher. He had one older sister. He started studying piano when he was eight, and he sang in his elementary school choir. Although he studied for mathematics entrance exams, in the summer of 1989 he began his vocal training at the University of Music and Performing Arts Munich. While he was studying, he sang some small roles at the Bavarian State Opera. He graduated from university in 1994, achieving distinctions in both opera and concert performances.
He began his professional career at the Staatstheater Saarbrücken in 1994 and was soon invited to make debuts in German theaters such as the Stuttgart Opera and Hamburg State Opera, as well as international debuts at the Lyric Opera of Chicago, Opéra National de Paris, and La Scala. He made his Salzburg Festival debut in 1999 in a new production of Busoni's Doktor Faust and returned there in 2003 as Belmonte in Mozart's Die Entführung aus dem Serail and for concerts of Beethoven's Ninth Symphony with the Berlin Philharmonic.