Objective: To evaluate potential risk-factors of ADHD among primary school-children (PSC) in state schools in Colombo district of Sri Lanka. Method: A case-control study was conducted with 73 cases and 264 controls selected randomly among 6 to 10-year-old PSC from Sinhala medium state schools in Colombo district. Primary care givers completed the SNAPIV P/T-S scale to screen for ADHD and an interviewer-administered questionnaire on risk-factors. Children's diagnostic status was confirmed by a Consultant Child and Adolescent Psychiatrist based on DSM-5 criteria. Results: A binomial regression model identified male sex (aOR = 3.45; 95% CI [1.65, 7.18]), lower educational level of the mother (aOR = 2.99; 95% CI [1.31, 6.48]), birth weight <2,500 g (aOR = 2.83; 95% CI [1.17, 6.81]),a neonatal complications (aOR = 3.82; 95% CI [191, 7.65]) and child having witnessed verbal/emotional aggression between parents (aOR = 2.08; 95% CI [1.01, 4.27]) as significant predictors of ADHD. Conclusion: Primary prevention should focus on strengthening neonatal, maternal and child health services within the country.