The study focuses on teachers' beliefs regarding the malleability of their teaching ability. It examines the relationships among teachers' growth mindset, flow, critically reflective behavior (CRB) and burnout. Whereas educational studies tend to focus more on teachers' behaviors rather than on their beliefs and feelings, the current study aims to deepen our understanding of the latter. Responses from 281 teachers to online questionnaires provided support to the majority of the research hypotheses. Teachers with a growth mindset were more likely to experience flow, practice CRB and feel less burnout. Moreover, the relationship between teachers' growth mindset and burnout was fully mediated by both flow and CRB, and flow partially mediated the growth mindset-CRB relationship. The findings imply that teachers with a growth mindset tend to experience higher levels of flow, practice more CRB and feel less burnout, suggesting that flow and CRB may explain these connections. The study contributes to the literature on teachers' mindsets and their professional behavior, and offers several implications to the theory and practice of teachers' professional development.