Background <p>Somatic pain and depression are prevalent health concerns among Chinese adolescents. This study aims to examine the longitudinal reciprocal effects between these conditions in this population, explore the moderating role of gender, and propose recommendations to improve adolescent health.</p> Materials and methods <p>Utilizing a cross-lagged design, this longitudinal study tracked a convenience sample of seventh- and eighth-grade students (aged 12–16) from two middle schools in Sichuan between April 2023 and April 2024. Measures included the Patient Health Questionnaire (PHQ-9) to assess depression and a five-item somatic pain scale. Analytical methods comprised descriptive statistics, Harman’s single-factor test, correlation analyses, t-tests, and structural equation modeling.</p> Results <p>Cross-lagged analyses reveal a dynamic interplay between somatic pain and depression over time among Chinese adolescents, with gender serving as a significant moderator in this reciprocal relationship. Specifically, among adolescent boys, depression predicts somatic pain over a one-year interval, and somatic pain similarly predicts depression. In contrast, among adolescent girls, depression unidirectionally predicts somatic pain over the same period, with no significant effect observed in the reverse direction. Additionally, the association between somatic pain and depression is significantly stronger in adolescent girls than in boys at both time points. Furthermore, adolescent girls report higher levels of both somatic pain and depression compared to boys at both time points.</p> Conclusion <p>Somatic pain and depression exhibit a dynamic interplay over time among Chinese adolescents, with gender significantly moderating their reciprocal relationship. These findings highlight the need for gender-specific intervention strategies and underscore the importance of addressing both somatic pain and depressive symptoms with equal priority in adolescent health management programs.</p>