She holds the title Kammersängerin from the Bavarian State Opera in Munich and the Vienna Staatsoper.

Fassbaender was born in Berlin, the daughter of screen actress Sabine Peters and baritone Willi Domgraf-Fassbaender.

She joined the Bavarian State Opera in 1961, where her first leading role was Nicklausse in The Tales of Hoffmann.

[4] She has appeared in numerous televised opera productions now available on DVD, such as her signature roles Octavian and Orlofsky, both conducted by her frequent collaborator Carlos Kleiber.

In 1999, she became intendant (managing director) of the Tiroler Landestheater (Tyrolean State Theatre) in Innsbruck, a position she held until 2012.