This paper describes how improving a teacher's content knowledge changes his teaching practices and its subsequent effects on student learning during a middle school volleyball instructional unit. The study was designed to challenge teacher educators' thinking about the importance of in-depth content knowledge for effective teaching by demonstrating the effects of a content knowledge workshop on a teacher's teaching practices and student learning. A mixed-method research design was adopted with one male physical education teacher's qualitative teaching data and his 24 eighth-grade students' quantitative learning data. Two separate classes of volleyball were observed for 5 days before and after the content knowledge workshop (n = 20 lessons total). Audio and videotaped recordings were made of each lesson. Descriptive and constant comparative analyses were used to analyze the data. The results of the study indicated that the teacher used more task progressions, integrated skill practices, small-sided games, content adaptations, and diverse verbal instructional repertoires after developing content knowledge. These changes ultimately impacted the students' game performance and involvement as well as cognitive understanding of content. The findings verify that there are strong relationships among the teacher, content, and student learning by showing how the other components are changed when the teacher's level of content knowledge is altered. The research effort may guide teacher educators' professional development efforts aimed at increasing pre-service and in-service teachers' professional knowledge for teaching.