Teacher well-being is a critical factor affecting job performance and thus, significant for enhancing quality teaching. Based on the job demands-resources model, this study examines the mediating effects of teachers' self-monitoring and self-efficacy on the relationships between the emotional job demands of teaching and trust in colleagues and teacher well-being. A questionnaire was administered to 1115 primary school teachers in Hong Kong. The results highlight the maladaptive role of self-monitoring as a personal demand and the adaptive role of self-efficacy as a personal resource: self-monitoring is positively related to anxiety and depression; self-efficacy is positively related to enthusiasm and contentment and negatively related to anxiety and depression. The results not only support the beneficial role of trust in colleagues, which is positively associated with teacher self-efficacy and well-being, but also reveal the rewarding side of emotional job demands in enhancing teacher self-efficacy. Theoretical contributions and practical implications are discussed.