Background <p>Various events shape the professional journey of health professions teachers. Among these, critical incidents are critical due to their psychological impact, which can influence teachers’ insights and academic performance. This study aimed to identify them at Tehran University of Medical Sciences.</p> Methods <p>A qualitative approach was employed, using semi-structured interviews with 22 faculty members (to ensure diversity). Data were analyzed using conventional content analysis, based on Elo and Kyngäs’s framework, in three stages.</p> Results <p>A total of 247 initial codes were extracted, which, after merging and refinement, resulted in 83 critical incidents categorized into six general categories: critical incidents related to students; teachers’ responsibilities; colleagues, managers, and officials; the organization; and society. In this study, 72 codes were extracted for critical incidents with negative valence, and 15 for those with positive valence in identified categories.</p> Discussion <p>Various sources can lead to critical incidents in the professional lives of health profession teachers. In addition to issues such as professional responsibilities and interactions with students, numerous sources—including administrators and officials, other teachers and peers, the organization, and even society—are determinants of fateful and influential situations that can involve a teacher for long periods and affect their performance.</p> Conclusions <p>This study highlights the complexity of teacher identity and emphasizes the shared responsibility for supporting teachers’ performance, offering deeper insight into their professional journey in health sciences universities.</p>