Stefanie Bredthauer studied linguistics, Dutch language and literature and business administration. Her exam thesis dealt with transfer influences of first language and first foreign language when learning German as a tertiary language. Afterwards she did her doctorate on linguistic disguise in blackmail letters and other incriminated texts using a data corpus of the Federal Criminal Police Office. During her doctorate, she worked at an international training centre as a lecturer for German as a second and foreign language and as a quality manager. In the years 2010 to 2015, she worked as a research associate at the Department of Intercultural Communication and Multilingualism Research at the University of Bonn, taking over the team leadership of the language learning centre.

Since December 2015, she has been working as a researcher in various research projects at the Mercator Institute, and since March 2019 she is leading the research group Multilingual Learning Groups. Her research focuses on multilingual didactics, individual multilingualism, German as a second and foreign language, and second and foreign language didactics in general. She is doing her habilitation thesis on the topic of Multilingualism in the Classroom - Didactics and Implementation.