When the Nazis came to power in 1933, Giehse left Germany for Zürich, Switzerland, where she continued to act in exile, playing leading roles in Zürich, including in Erika Mann's acclaimed political cabaret the Pfeffermühle (which was itself also an exile, having been transported from Munich to Zürich in 1933 as well). During her exile, she traveled throughout central Europe with Pfeffermühle. On May 20, 1936 she married the homosexual, English writer John Hampson in order to obtain a British passport and thereby avoid capture by the Nazis. She returned to Germany after World War II, and performed in theatres on both sides of the Iron Curtain, but mostly in her native Bavaria, until her death in 1975.
After the war, Giehse returned to Munich and to the Munich Kammerspiele, where, in 1950, she again played the role of Mother Courage, this time directed by Brecht himself. This production became documented as the second "Model production" of Brecht's play (the first "Model production" had been performed by Brecht's wife, Helene Weigel in 1949 in Berlin). Giehse and Brecht would often converse in their strong Bavarian (southern German) dialect during rehearsals, making Brecht's wife jealous of their kindred spirit.
In the 1950's, Giehse played several roles as a member of Brecht's theatre, the Berliner Ensemble. In the mid 1970's, Therese Giehse returned to the Berliner Ensemble to perform several Brecht Evenings of the poems, plays, and writings of her lifelong friend and colleague, the late Bertolt Brecht. As a member of the Berliner Ensemble and collaborator with Brecht, she was a much-sought-after interpreter of his work and recordings of her reciting and singing his work appeared on records in both East and West Germany
Throughout the 1950's and 1960's, Giehse continued to perform many lead roles in various theatres in Germany, often using her considerable comic skills to play character roles, as well as great dramatic roles, such as the leads in several landmark productions by Friedrich Dürrenmatt, the world premiere of The Visit in 1956, and The Physicists in 1962. Later, she also worked with Peter Stein's renowned Schaubühne am Halleschen Ufer in Berlin.
She also appeared in over 20 films and a number of television productions.
In 1988, a commemorative stamp was printed in her honor as part of the Women in German history series.