The purposes of this study were twofold: to examine the effects of a community of practice (CoP) on (1) physical educators' and their students' health-related fitness content knowledge and (2) the physical educators' health-related fitness pedagogical content knowledge construction process. Twelve experienced physical education teachers (six in treatment, six in control group) and 278 of their students voluntarily participated in this study. Mixed method research with experimental pre-post design was used. Quantitative analysis of health-related fitness tests data used descriptive statistics, repeated measure ANOVAs and simple main effect analysis. Semi-structured post interviews with teachers and CoP facilitator, researcher field notes and audio taped and fully transcribed text of six week CoP represented the qualitative data sources that were analysed through Glaser and Strauss' (1967) constant comparison approach. Results demonstrated that treatment group teachers and their students improved health-related fitness content knowledge from pre to post test (p less than 0.05). Findings indicated that teacher participation in a CoP changed their teaching practices and teaching culture by focusing on their students' needs, increased their engagement in physical education and triggered continued learning toward personal professional needs. In conclusion, this study indicates that a CoP based on teachers' specific needs increased their students' learning and changed teachers' teaching culture positively. (Contains 2 tables and 1 figure.)