Her career proceeded, when in 1926, she became a member of the New German Theatre ensemble in Prague, where she and her future husband Attila Hörbiger (1896–1987) performed in Les Nouveaux Messieurs by Flers and Croisset.

After being denied the role of Jenny in Brecht's Threepenny Opera in 1929, she quit and joined the ensemble of the Theater in der Josefstadt under director Max Reinhardt.

In 1932, she appeared in Hauptmann's Rose Bernd under director Karlheinz Martin at the Deutsches Theater in Berlin, acclaimed by the audience as well as by critics like Alfred Kerr and colleagues like Werner Krauss.

On 23 December 1932, having taken singing lessons, she played the leading role in the premiere of Fritz Kreisler's Singspiel Sissy at the Theater an der Wien.

Wessely, who was not particularly photogenic, was passed over in favor of Magda Schneider for the role of Christine in Max Ophüls' 1933 film version of Arthur Schnitzler's Liebelei, a part she had played at Theater in der Josefstadt.

She resumed her career in 1945 at the Innsbruck State Theatre with the role of Christine in Liebelei, and again at the Theater in der Josefstadt in Brecht's The Good Person of Szechwan the next year.