AbstractAlthough the subject-specific professional knowledge of teachers is considered to be of central importance with regard to the learning performance of their students, there is only sparse empirical evidence on this issue. Moreover, current studies are primarily limited to the subject of mathematics. The aim of this article is to investigate the significance of subject-specific professional knowledge and skills of physical education (PE) teachers on the practical learning gains of their students based on a panel study. In order to measure both non-contextual knowledge and contextual skills on the teachers’ side, paper–pencil tests as well as video and text vignettes were used as test instruments. On the students’ side, practical sport skills were assessed in a pretest–posttest design to evaluate competence growth with regard to complex sports performance. An effect chain with mediation processes was postulated. Multilevel modeling analyzing 1669 students who were taught by 74 teachers could prove significant performance improvements for the students, but none of the four differentiated knowledge dimensions (content knowledge, non-contextual; pedagogical content knowledge, non-contextual; content knowledge, contextual; pedagogical content knowledge, contextual) of the teachers could explain these learning gains. Thus, the results are in line with various studies in mathematics and suggest that direct effects of teachers’ professional knowledge on students’ learning gains seem to be lost. The results therefore suggest that while basic and broad professional knowledge is required for instructional success, specific expertise in certain competence areas does not lead to additional learning success among students. Further research within the EPiC-PE study is needed to provide a more comprehensive picture of the relationships between professional knowledge and skills, classroom behavior, instructional processes, and learning outcomes.