Background <p>Self-concept clarity and mindfulness have gained increasing attention in educational and psychological research, as they are considered important variables in explaining differences in students’ levels of academic engagement. However, the moderating role of psychological capital in this relationship remains insufficiently understood.</p> Objectives <p>This study examines the mediating role of self-concept clarity in the association between mindfulness and academic engagement, and the moderating role of psychological capital in this pathway.</p> Methods <p>A total of 503 medical students from Shandong Xiehe University, Jinan, China, participated in the study and completed the Cognitive and Affective Mindfulness Scale–Revised (CAMS-R), the Utrecht Work Engagement Scale for Students (UWES-S), the Self-Concept Clarity Scale (SCCS), and the Student Psychological Capital Questionnaire (PCQ).</p> Results <p>Analysis revealed that self-concept clarity partially mediated the relationship between mindfulness and academic engagement. The mediation model explained 11.0% of the variance in academic engagement (R² = .1102, F(5, 497) = 12.31, <i>p</i> &lt; .001), and the interaction term accounted for an additional 1.2% of explained variance (ΔR² = .0123, <i>p</i> = .007). In addition, psychological capital moderated the relationship between mindfulness and self-concept clarity, thereby strengthening this indirect pathway and contributing to higher levels of academic engagement.</p> Conclusion <p>These findings provide evidence for the psychological mechanisms underlying student engagement and offer practical implications for medical education, including the development of mindfulness-based interventions and strategies to enhance psychological capital among medical students.</p>