Introduction: Adverse Childhood Experiences (ACEs) are traumatic events, including abuse and household dysfunction, experienced by children and adolescents. ACEs trigger stress, alter brain development and lead to long-term health problems among adolescents. Objectives: To describe the associations between ACEs and health risk behaviours among 16- 17-year-old school-going adolescents in Vavuniya district, Sri Lanka. Methods: A cross-sectional study was conducted among 16-17-year-old school-going adolescents in Vavuniya district, Sri Lanka, using a pre-tested self-administered questionnaire. ACE questions were adapted from 17-item Paediatric ACEs Screening and Related Life-events Screener which covered ACEs including exposure to discrimination, food insecurity , housing instability , community violence, caregiver illness/disability , and separation from caregivers. Ethical approval was obtained and the data were analysed using the chi-square test. Results: A total of 461 adolescents were recruited. The majority were Tamil (73.1%), and 79.6% reported having both parents as caregivers. Over half (57%) had experienced at least one ACE. Reported prevalence of risk behaviours were; smoking-4.6%, alcohol consumption-5.6%, and substance use-2.6%. 10% reported being bullied at school, 23.4% experienced cognitive difficulties, and 28.6% reported depressed mood. ACEs were significantly higher among children without both parents (p