Background: Factors contributing to the relief of depression among adolescents have not been sufficiently revealed. The aim of this study was to assess the effect of teacher support on depression in adolescent students. Methods: We conducted a self-rating questionnaire survey among 2862 junior high school students and 93 homeroom teachers in Japan. We employed binary logistic regression models, with teacher support averaged for each class as an explanatory variable and depression as an objective variable. To examine the interaction terms of class average score for teacher support by economic status, by student sex, and by grade satisfaction were estimated. Results: Higher class average scores for teacher support were independently associated with lower levels of depression among adolescents (odds ratio [OR], 0.739; 95% confidence interval [CI], 0.575-0.948). Furthermore, the interaction of class average scores for teacher support with grade satisfaction was significant (p?= 0.025). The interaction of class average score for teacher support with economic status and with student sex was not significant. Conclusions: Our findings suggest that higher class average scores for teacher support were significantly associated with lower depression. These results can help homeroom teachers enhance interventions and promote the health of their homeroom students.