Theresa Horejsi was born into a family of musicians in 1999. Starting with the violin, she often took part in the "Jugend Musiziert" competition and gained experience in orchestras and chamber music ensembles from an early age. She discovered the viola through her family.

She studied from 2018 at the Cologne University of Music and Dance in the class of Matthias Buchholz and is currently studying at the haute ecole de Musique de Lausanne with Tatjana Masurenko.

She has worked as a chamber musician with Jörg Widmann, the Minguett Quartet, Harald Schoneweg, Gregor Schwellenbach, Robert Kulek and Daniel Haefliger. She has participated in recordings for the Arte Film "TRANS - I Got Life", which was broadcast on television in September 2023.

In September 2023, she took part in the prestigious ARD Music Competition. In March 2024, she takes up a 3. Soloposition in the St. Gallen Symphony Orchestra.