This study aimed to investigate the symptoms of trauma, depression, anxiety, and irritability in children with attention deficit hyperactivity disorder (ADHD) during home confinement due to COVID-19. The sample of this single-center, cross-sectional study consisted of 42 children with ADHD and their parents. There were significant differences in the severity of depression, anxiety, irritability, and ADHD symptoms between the group that experienced pathological trauma reactions and the group that did not. According to the results of mediation analyses, the irritability score was found to be the full mediating factor in the relationship between trauma reaction scores/emotional symptom scores and the severity of ADHD symptoms. Because of the modest sample size due to the exclusion of ADHD patients with comorbidities, we recommend that future research focus on reproducing the role of irritability, in larger samples, as the full mediator on the path from cognition to behavior in children with ADHD under home confinement during the pandemic.