Background: Adolescent mood disorders (MD) have become an important public health problem worldwide. However, the psychopathological mechanisms underlying the occurrence of adolescent MD remain poorly elucidated.Therefore, in this study, we explored the mediating role of psychological resilience in the effects of rumination on depression in Chinese adolescents with MD. Methods: A total of 569 adolescent MD patients were included. Recruitment took place between October 2019 and June 2022. The Patient Health Questionnaire-9 (PHQ-9) was used to assess depressive symptoms.The 21-item Chinese version of the Ruminative Responses Scale (RRS) was used to assess rumination, and the 10 -item Chinese version of the Connor-Davidson Resilience Scale (CD-RISC-10) was used to measure psychological resilience. Results: The prevalence of MD in adolescents with severe depressive symptoms (SDS) was 46.05%. The prevalence of SDS was much higher in females (50.75%) than in males (35.09%).The prevalence of SDS was much higher in adolescents with MD living with grandparents (56.25%) and living in single-parent families (61.36%) than in those living with parents (43.00%) and those having one parent who was away fora long time (40.00%). Adolescents with MD and also with SDS had higher levels of rumination and lower levels of psychological resilience than adolescents without SDS. Resilience partially mediated the relationship between rumination and depression. Conclusions: Living style influences the severity of depressive symptoms in adolescents with MD. Rumination and psychological resilience were the risk and protective factors for SDS in adolescents with MD, respectively. Furthermore, resilience can reduce the impact of rumination on depressive symptoms, suggesting that clinical interventions to improve patients' resilience and reduce rumination may be a viable consideration for adolescents with MD.