In 1953, Sebaldt made her film debut alongside Rudolf Prack in When The Village Music Plays on Sunday Nights.

She played in music films like The Gypsy Baron, dramas like The Story of Anastasia (with Lilli Palmer in the title role), comedies like Helmut Käutner's The Zürich Engagement (with Lilo Pulver) and Father, Mother and Nine Children (with Heinz Erhardt), crime fiction like The Black Sheep after Gilbert Keith Chesterton (with Heinz Rühmann as Father Brown), and the gangster movie parody Oops, here's Eddie!

She often embodied sympathetic characters, but also cunning gangsters such as Virginia Peng in the real-life version of Manfred Schmidt's popular comic series Nick Knatterton.

In addition, she had numerous guest appearances in series such as Tatort, Das Traumschiff, Der Kommissar, Derrick and The Old Fox.

In addition, Sebaldt worked extensively for radio (NDR, RIAS, SFB), and was the German voice for internationally renowned actresses as Antonella Lualdi (The Red and the Black), Eva Marie Saint (A Hatful of Rain) and Joanne Woodward (Rally Round the Flag, Boys!