Objective: To explore the mediating role of balanced time perspective in the relationship between social jetlag and depressive symptom among junior high school students, so as to privide a basis for improving their mental health. Methods: In October 2024, a method of combining convenient sampling with cluster sampling was used to select 3 438 junior high school students from two districts(Yubei District and Kaizhou District) in Chongqing. The Center for Epidemiological Studies Depression Scale (CES-D), Munich Chronotype Questionnaire (MCTQ), and Balanced Time Perspective Inventory (BTPI) were administered for the survey. Statistical analyses included t-test, ANOVA, and Spearman correlation analysis, and conduct a mediation effect analysis using the Process program. Results: The mean score of depressive symptom among junior high school students was 15.00(9.00, 23.00 ), social jetlag was 1.18(0.72, 1.83) hours, and balanced time perspective score was -0.18(-2.82, 2.93). Social jetlag among junior high school students was positively correlated with depressive symptom score ( r =0.17), while balanced time perspective was negatively correlated with social jetlag ( r =-0.15) and depressive symptom score ( r =-0.68) (all P <0.01). Mediation analysis showed that balanced time perspective partially mediated the relationship between social jetlag and depressive symptom ( β=0.68, P <0.01) among junior high school students, accounting for 53.97% of the total effect. Conclusions Social jetlag of junior high school students influences depressive symptoms by affecting balanced time perspective. Efforts should be made to improve adolescents balanced time perspective for reducing the impact of social jetlag on depressive symptom.