A retrospective chart study of patients on open-label aripiprazole treatment was conducted in the Netherlands to add to the knowledge of aripiprazole in children and young adults with mild and borderline intellectual disabilities (IDs). Fifty-three youths, mean age 14.7 ± 3.4 years and mean IQ 64.5 ±13.8, were included. Treatment responders were defined as “much improved” or “very much improved” based on the Clinical Global Impression -Improvement scale. For 83% of the patients, disruptive behavior was the main target symptom. The overall response rate was 30% after 1–4 weeks and 69% after 5–8 weeks. The 5–8 weeks responders showed a response rate of 64% at 22–26 weeks. Mild adverse events were observed in 53% of the patients of which fatigue and weight gain were the most common. Seven patients (13.2%) discontinued because of adverse events. In 53 children and young adults with mild and borderline IDs, aripiprazole was effective in both the short and the long term. No serious adverse events were observed.