Sonja Beißwenger initially studied Ethnology, Journalism, and Philosophy before completing her acting training at the Hanover University of Music, Drama and Media (HMTMH) from 2001 to 2004.
While still a student, she joined Schauspiel Hannover in 2003, where she appeared in numerous productions, including Goethe's Faust I & II, directed by Sebastian Baumgarten, in which she performed the role of Mephisto. Two productions in which she appeared—Hotel Paraiso by Lutz Hübner, directed by Barbara Bürk (2004), and Simon Stephens' Pornography, directed by Sebastian Nübling (2007)—were invited to the prestigious Berlin Theatertreffen. For her performance as Wendla in Spring Awakening, adapted and directed by Nuran Calis, she received the Emerging Artist Award.
In 2009, she followed artistic director Wilfried Schulz to Staatsschauspiel Dresden, where she remained a member of the ensemble for six seasons. In 2011, Schiller's Don Carlos, directed by Roger Vontobel, was invited to the Berlin Theatertreffen. For her portrayal of Electra in Sartre's The Flies, directed by Andreas Kriegenburg, she was awarded the Erich Ponto Prize for Outstanding Artistic Achievement.
In 2014, she appeared in Horváth's Don Juan Comes Back from the War, directed by Andreas Kriegenburg, at the Salzburg Festival. The following year, she performed as Polly in Mackie Messer – A Salzburg Threepenny Opera, directed by Sven-Eric Bechtolf and Julian Crouch.
Since 2015, Sonja Beißwenger has worked as a freelance actress. Alongside her stage career, she has established herself as a voice artist and performer in literary readings, radio, and film, with a particular passion for music-based productions. She collaborates regularly with a variety of musical ensembles, including an ongoing concert series with the NDR Radiophilharmonie. She also teaches acting at both the Folkwang University of the Arts and the Hanover University of Music, Drama and Media.
From 2016 to 2026, she was a regular guest artist at Düsseldorfer Schauspielhaus, where her roles included Marla Singer in Fight Club, adapted from Chuck Palahniuk's novel, and Stauffacher in Schiller's William Tell, both directed by Roger Vontobel; Margaretha di Napoli in Henry VI & Margaretha di Napoli, Tom Lanoye's adaptation after Shakespeare, and Petra von Kant in Rainer Werner Fassbinder's The Bitter Tears of Petra von Kant, both directed by David Bösch; Franziska in Frank Wedekind's Franziska, directed by Sebastian Baumgarten; and The Other in Wolfgang Borchert's The Man Outside, directed by Adrian Figueroa.
From 2022 to 2025, she appeared as a cover performer for the roles of Polly, Jenny, and Lucy in The Threepenny Opera, directed by Barrie Kosky, at Berliner Ensemble.
During the 2023/2024 season, she appeared at Schauspiel Frankfurt as Orlando in a stage adaptation of Virginia Woolf's novel, directed by Katrin Spira and Anselm Weber.
Since 2025, she has been performing in Der Schneesturm (The Blizzard), based on the novel by Vladimir Sorokin and directed by Kirill Serebrennikov, with performances including Düsseldorfer Schauspielhaus and the Salzburg Festival.