<p>This mixed-methods study investigated burnout factors in Chinese secondary school teachers. Quantitative data from 620 teachers, collected via self-report measures of professional identity, psychological capital (PsyCap), self-regulation, and burnout, were analyzed alongside qualitative data from Critical Incident Technique (CIT) interviews with 25 teachers. Statistical analysis validated the measures used. Quantitative results indicated that stronger professional identity and higher PsyCap were significantly associated with lower burnout. Professional identity also positively predicted PsyCap. Self-regulation emerged as a key mediator in these relationships, suggesting that professional identity and PsyCap enhance teachers’ self-regulation skills, thereby reducing burnout. Additionally, a chain mediation effect was identified: professional identity indirectly reduced burnout through PsyCap and subsequently self-regulation. Qualitative findings provided nuanced insights into teachers’ experiences, highlighting workload overload, lack of support, and ineffective student engagement as challenges, and positive coping strategies as resilience mechanisms. These findings advance the understanding of Chinese teachers well-being and offer implications for policy and professional development. Supportive environments and programs fostering professional identity, PsyCap, and self-regulation can empower teachers to navigate professional challenges and promote a more sustainable and positive teaching experience.</p>