Adolescents often face interpersonal and adjustment challenges when transitioning from a family-centered to a school-based environment, especially without a supportive group climate. To address these challenges, this study used football, the world’s most widely played team sport, as a platform to examine the impact of athlete engagement on team cohesion and its underlying mechanisms. A total of 1692 Chinese adolescents who regularly participated in football training and demonstrated a strong passion for the sport were recruited. Data were collected using the Athlete Engagement Questionnaire (AEQ), the Interpersonal Competence Questionnaire (ICQ), the Perceived Workplace Social Support Scale (PWSSS), and the Group Environment Questionnaire (GEQ), all of which demonstrated good reliability and validity in this study. The results revealed that (1) athlete engagement was positively associated with team cohesion team cohesion; (2) interpersonal competence partially mediated the relationship between athlete engagement and team cohesion; (3) social support moderated both the direct relationship between athlete engagement and team cohesion and the indirect relationship between athlete engagement and interpersonal competence; and (4) social support moderated the relationship between athlete engagement and team cohesion with significant gender differences, whereas no gender differences were observed in the relationship between athlete engagement and interpersonal competence. This moderated mediation model not only enriches the conceptual model of group cohesion but also addresses gaps in the current literature. Furthermore, it provides theoretical support for physical educators to design targeted team sports interventions tailored to the characteristics of different gender groups.