Based at Deutsche Oper Berlin, she was in demand internationally, also as a singer of Lied and concert, a profilic performer of Bach's church cantata cycle conducted by Karl Richter.

[6] Between 1970 and 1972 she performed 25 times at the Metropolitan Opera in New York City, as Pamina in Die Zauberflöte, Marzelline in Fidelio, Ännchen in Weber's Der Freischütz and Zerlina in Don Giovanni.

[1][15] She performed at the Vienna State Opera, after Cherubino, also as Zerlina in Don Giovanni between 1972 and 1985, Sophie in Der Rosenkavalier by Richard Strauss, Susanna in Figaro between 1976 and 1986, and Pamina.

[6] "Sull'aria...che soave zeffiretto", a duet from Le nozze di Figaro that she performed with Gundula Janowitz as the Countess, features prominently in the film The Shawshank Redemption.

[2][9][21] Mozart roles were among Mathis' specialities, including Cherubino in Le nozze di Figaro, Zerlina in Don Giovanni, Despina in Così fan tutte and Pamina in Die Zauberflöte.

[22] Her recorded Mozart roles include Susanna in Le nozze di Figaro for the Deutsche Oper Berlin with Karl Böhm conducting,[23] and Ilia in Idomeneo with the Staatskapelle Dresden.

[24] A re-released recording of Don Giovanni with the Vienna Philharmonic and Karl Böhm from the 1977 Salzburg Festival features her in one of her best-known roles, Zerlina.

[17][26] Mathis made many recordings of Lied repertoire, by Mozart in 1973 with Bernhard Klee and in 1986 with Karl Engel,[53] by Schumann with Christoph Eschenbach,[54] also by Schubert,[55] Richard Strauss and Hugo Wolf.