Attention-Deficit/Hyperactivity Disorder (ADHD) is a persistent pattern of behaviours characterized by inattention, hyperactivity and impulsivity. This study evaluates the effects of a tailored Incredible Years Teacher Classroom Management (IYTCM) programme aimed to improve participating children's on-task behaviour in a group of 6 to 10 year old children with ADHD in Addis Ababa, Ethiopia. The effectiveness of the IYTCM programme has been extensively examined for children with conduct disorder and/or behaviour and emotional issues, but not specifically with children with ADHD. In the present study, the effects of the IYTCM were examined on individual children with ADHD symptoms. Nine children identified with ADHD symptoms on the basis of teacher and parent reports of behaviour and nine normative comparison children were also selected from the same classrooms. Ten teachers received the tailored IYTCM-ADHD training for about 36 hours. A single-subject design was implemented to record the behaviour changes over time: at baseline, during teacher training with the IYTCM-ADHD programme, and at both immediate and long-term follow-ups. In addition to visual analysis, a non-parametric test was used to examine the magnitude of effect in each child. The result of the study indicated that the on-task behaviour of participating children with ADHD increased by the conclusion of the study ranging from 46% to 100%. Visual analysis also indicated that the children's behaviour was maintained during the follow-up phases. The pre- and post-intervention analyses of children with ADHD showed a significant effect of the intervention on each child. In light of the findings, limitations and implications for future research are discussed.