More and more children and adolescents in Switzerland show serious deficits in their German language skills. In order to specifically promote the language skills of students with a non-German first language, special lessons in German as a second language (GasL) are therefore offered in addition to the regular lessons. The aim of this case study is to evaluate the impact of a pedagogically sound immersive virtual reality learning unit for GasL lessons, which offers students the opportunity to actively speak German and to demonstrate this in the context of two GasL lessons. The research design is based on the "Design Science Research Framework". In this context, the virtual reality learning unit was designed as an innovative prototype (artifact) and iteratively improved. The design considered the didactic framework of the official curriculum as well as the eleven general design guidelines for virtual reality learning units in an educational context. The virtual reality learning unit was tested in a field experiment with five students each at an elementary school and at a secondary school. The students found the virtual reality learning unit as a whole attractive and motivating. But there are operational challenges and necessary prerequisites that have to be considered and created in order to pragmatically and sustainably integrate immersive virtual reality learning units into the existing GasL lessons.