Background: Adolescents is an age group between 10-19 years of life and in India every 5th person is graded under adolescent category, and it is very precious, dynamic phase of adaptation for every individual they learn and adopt behaviour patterns which determines their future health determinants i.e. physical, social and mental. For a healthy development the adolescents require to practice healthy behavior, due to unavoidable circumstances in life of adolescents they possess certain high-riskbehaviors that affects their physical, emotional and social develop. Objective: To assess the high-risk behaviour among adolescents studying in schools of district Gurugram, Haryana. Methods: A quantitative approach and a cross sectional design was adopted. The study was conducted in selected schools of district Gurugram, Haryana, through convenient sampling technique 200 adolescents with the age group 10 -19 years were selected for the study. Data was collected using sociodemographic data sheet and standardized WHO, global school-based student health survey core questionnaire, GSHS(2021). Result: In the present study majority of students 66.5% were between the age group of 18–19-year, alcohol use among adolescent concluded as low risk, 81% of adolescents were at low risk of unhealthy dietary behaviour and 19% at medium risk. all the adolescents were at low risk of drug use, Majority 73% were maintaining good hygiene, 77.5%, have poor mental health, 88.5% and 11.5% of the adolescents are having low and moderate risk of physical activity, 79.5% and 16% of the adolescents were having medium, and low protective factors, 93.5%, were having low risk of sexual behaviour, all the adolescents were at low risk of tobacco use and risk of violence and unintentional injuries. Conclusion: This study reveals that adolescents were vulnerable to high-riskbehaviors. Hence health camps, seminars, workshop and health education programme can be organized on high-risk behaviour and its impact on physical, emotional, social and academic activities by involving adolescents.