Background: Patients with intellectual disability in psychiatric services are rarely asked about their experiences when admitted to inpatient units. Aim: To enhance the understanding of ward atmosphere for inpatients with co-occurring intellectual disabilities (ID) and mental illness by exploring patients’ experiences from a specialised mental health inpatient unit. Methods: A selected sample of 10 adults with comorbid mental illness and ID were recruited for a qualitative interview study based on Gunderson’s conceptualisation of therapeutic components in mental health wards. The patients were interviewed by two experienced clinicians and interviews were analysed using directed content analysis. Results: Patients’ experience of their relationships with ward staff seemed central to their experiences of several aspects of mental health nursing. Feeling safe, contained, and validated, were further important aspects. However, the patients seemed to have little influence on treatment choices and did not report participating in shared decision-making. Conclusions: The patients’ answers in this study are in line with previous research on ward atmosphere for patients in the general population. However, more research is necessary to inform future mental health nursing for patients with ID, both in inpatient and ambulatory services.