The purpose of the study was the evaluation of a teacher in-service training program, namely “PE.T.Co.N.“, an online community of practice via Facebook groups. Drawing from Self-Determination theory (SDT), the program aimed at satisfying teachers’ autonomy, competence, and relatedness needs and facilitating their autonomous motivation. Pre-post measurements showed significant improvements in key variables that can determine training success. Preliminary quantitative group insights supported by qualitative data revealed enhanced participatory dynamics in terms of members’ interaction. Findings suggest that PE.T.Co.N. is a promising, innovative approach to teacher training. Implications are discussed in light of SDT. •PE teacher in-service training can be delivered effectively as a CoP through Facebook groups.•Facebook appears a promising tool to tackle the attrition issue in on-line training.•PETCoN participation leads/contributes to increased autonomy need satisfaction.•PETCoN increases relatedness need satisfaction and decreases relatedness frustration.•Self-determination theory is well suited when designing teacher in-service training.