Objective: The aim of this study is to determine the prevalence and related risk factors of possible depression for high school students in Silivri, and to emphasize the importance in terms of public health. Methods: This cross-sectional study conducted with 680 high school students. Data was collected by performing a questionnaire between November 2017-January 2018. “Beck Depression Inventory” and “Sociodemographic Data Form” consist of 34 questions were applied to students. Results: Possible depression ratio was 33.2%, (95% CI= 29,7-36,8) mean BDI score was 13.3. Women were 3.0 times more likely to be at risk of possible depression than men. Possible depression was more common in the nine and eleventh grade students, those whose parents living separately , those with extended and dispersed families . Similarly, possible depression was more common in those who had physical activity 0-1 days a week, without regular hobby, with sleep disorder, did not sleep as long as recommended hours, skip meal, did not have breakfast at home in school days, with chronic disease, with regular medication, with history of depression, with chronic/mental illness in family history. Conclusion: Gender, class, family type, physical activity, sleep duration, skipping meals, presence of chronic disease in family were important factors to predict possible depression. Assessment of depression prevalence and associated factors is important for improving adolescent health and protective mental health. Precautions should be taken to prevent psychiatric disorders in adolescents, such diseases should be screened in schools, and students should be directed to psychologist/psychiatrist when necessary.