Scientific inquiry has been advocated as a common curriculum goal in school science education in South Africa, and also throughout the world. In South Africa, the introduction of inquiry-based instruction in a reformed science curriculum has met with serious challenges, such as the under-preparedness of in-service teachers. The purpose of this study was to capture, portray and develop the pedagogical practice of Physical Sciences teachers in inquiry-based teaching using an empowerment evaluation approach. The study is a multiple case study in inquiry-based teaching of three Physical Sciences teachers in South Africa using a mixed methods design. Empowerment evaluation is the use of evaluation concepts, techniques, and findings to foster improvement and self-determination. Underlying an inquiry-based pedagogy is the assumption that science education is not merely about knowing-acquisition, but understanding how scientific knowledge is generated, evaluation of knowledge claims and conducting scientific research. Data were collected by means of semi-structured interviews, a pedagogical orientation instrument, and classroom observations. The findings reveal that through empowerment evaluation, teacher practices in the classroom shifted towards an inquiry-based approach. The empowerment evaluation approach thus offers a viable and sustained form of professional development that is likely to empower teachers in assessing, planning, implementing and evaluating what they do.