Introduction: People with intellectual disability have a higher chance of developing mental disorders than the general population. Yet, few evidence-based interventions exist. This article evaluates My Lifestory, a narrative intervention tailored to people with intellectual disability and depressive or trauma-related complaints. Method: A quasi-experimental research design was adopted with an experimental condition (My Lifestory) and a matched control condition (care as usual). Measurements took place before the intervention, at the end of the intervention and at follow-up two months later. Measurements focused on psychiatric complaints, well-being, life satisfaction, mastery, and purpose in life. Results: Participants in the intervention condition improved more in psychiatric complaints, well-being, life satisfaction, and purpose in life, but not in mastery, than participants in the control condition. Effect sizes were large in the intervention condition and small in the control condition. Discussion: Despite some limitations, this study adds to the evidence base of this narrative intervention.