Although inquiry-based learning (IBL) has been a component of the Austrian curricula for chemistry for several years, it is implemented only rarely in schools. Even after attending a workshop-series regarding IBL teachers stated to not feel confident to implement IBL in their own classes. The professional development programme presented in this article aims to support teachers in gaining both experience and expertise in planning, applying and reflectingIBL in the framework of a Lesson Study. In collaboration with three chemistry teachers, a case study was conducted to identify useful structural elements as well as scaffolding strategies when implementing IBL in secondary chemistry classes. In addition, it is investigated in how far the professional development programme influences the teachers’ concept of IBL, their professional knowledge and skills, as well as their attitude towards IBL. In this article, the IBL units as well as the Lesson Study processare described in detail. The participating chemistry classes are characterised briefly and methods of data collection and data analysis are presented. Moreover, insights into first results are provided