Both ADHD and trauma exposure are common childhood problems, but there are few empirical data regarding the association between the two conditions. The aims of this study were to compare lifetime prevalence of trauma exposure in children with and without ADHD, and to explore the association between trauma exposure and outcomes in children with ADHD. Children aged 6-8 years with ADHD (n = 179) and controls (n = 212) recruited from 43 schools were assessed for ADHD, trauma exposure and comorbid mental health disorders using the Diagnostic Interview Schedule for Children IV. Outcome data were collected by direct child assessment, parent report and teacher-report, and included ADHD symptom severity, internalizing and externalizing problems, quality of life, and academic functioning. Logistic and linear regression models were used to examine differences adjusted for child and family socio-demographics. Children with ADHD were more likely than controls to have ever experienced a traumatic event (27 vs 16%; OR: 1.99; 95% CI 1.21, 3.27). This difference remained significant in the adjusted model (OR: 1.76, 95% CI 1.03, 3.01) accounting for child factors (age and gender) and family socio-demographic factors (parent age, parent high school completion and single parent status). Among those with ADHD, trauma-exposed children had higher parent-reported ADHD severity and more externalizing problems than non-exposed children, however, this effect attenuated in adjusted model. Children with ADHD were more likely to have experienced a traumatic event than controls. The high prevalence of trauma exposure in our sample suggests that clinicians should evaluate for trauma histories in children presenting with ADHD.