Purpose: Most of the current literature investigates workplace-based formal and informal learning separately; thus, the relationship between these two types of learning remains unclear. This study aims to fill this research gap, drawing on self-determination theory to bridge teachers' formal and informal learning and uncover the relationship between the two. Design/methodology/approach: The participants of the study are 1,886 primary and secondary in-service teachers in China. Structural equation modeling and bootstrapping are used to test the proposed model. Findings: The study reveals complicated influencing mechanisms of formal learning on different types of informal learning among in-service teachers. Teachers' basic psychological needs, satisfaction and challenge-seeking behavior are found to play crucial mediating roles in this process. Practical implications: First, this study suggests that different configurations of intervention strategies should be formulated depending on the foci for improving teachers' learning. Second, this study indicates that only highlighting the importance of reflection, which is the approach currently used, is not sufficient to improve teachers' daily reflective practice. Third, there is an urgent need to design training programs to improve teachers' abilities to purposefully expand their job boundaries, which could not only benefit teachers' performance but also contribute to school improvement. For policymakers and school principals, we suggest that more attention be given to the satisfaction of teachers' basic needs. Originality/value: This study contributes to the literature on workplace learning by connecting formal and informal learning and elucidating how teachers' reported formal learning influences their informal learning activities via varied paths. The findings have implications for continuous professional development policy and training programs in the workplace.