BACKGROUND: Engagement of individuals with an intellectual disability and their caregivers in health care has been highlighted as an essential factor in developing services that better meet client needs
however, few studies have focused on the engagement of individuals with a dual diagnosis (intellectual disability co-occurring with a mental health illness and/or challenging behaviour) in health care. METHODS: This qualitative participatory action study engaged clients and their caregivers in exploring principles and actions that can be applied to build active and meaningful engagement within a specialised community-based mental health service for adults with a dual diagnosis. RESULTS: The four themes that emerged from the data-Collaboration, Communication, Empowering Environment, and Tailored Service-offered a way to conceptualise client and caregiver engagement. CONCLUSION: This study underscores the importance of building a culture of service delivery that values, encourages, and supports client and caregiver engagement. Practical strategies for increasing engagement are provided.