Open-door policy is a recommended framework to reduce coercion in psychiatric wards. However, existing observational data might not fully capture potential increases in harm and use of coercion associated with open-door policies. In this first randomised controlled trial, we compared coercive practices in open-door policy and treatment-as-usual wards in an urban hospital setting. We hypothesised that the open-door policy would be non-inferior to treatment-as-usual on the proportion of patients exposed to coercive measures.