Introduction: Adolescence is a transitional period where inadequate/bad guidance may havenegative influences on self-esteem, emotional well-being, and values, with potential consequences including stress, anxiety, depression, and other behavioral issues that may negatively influence the future life of the individual. Objectives: To determine the prevalence and risk factors of stress, anxiety, and depression among school-going adolescents. Material and methods: The cross-sectional study is conducted among 462 Government school students of mid and late adolescence in the Kanchipuram district. The semi-structured questionnaire and DASS-21 scale were used to collect data on predictors and outcome variables. The epi-info 7 version was used to analyse data. The significance was tested using the Chi-square test and multivariate analysis. Results: The prevalence of stress, anxiety, and depression was 39.2%, 43.5% and 34.4% with a mild grade of severity being higher in all three outcomes. The students with poor academic satisfaction and low self-esteem were significant risk factors for all three outcomes. Students of joint and broken familiesand Poor academic performance was found to be significant risk factor for anxiety and depression. Adolescents with working mothers and the presence of parental alcohol use were found to be significant risk factors for depression. Conclusion: The high prevalence of any one of the stress, anxiety or depression reflects the need for periodical life skill sessions for adolescents and regular screening for mental health problems to be conducted in school.