A modified action research approach was used to implement a selected nursing model on a long-stay psychiatric ward. Within a broader quasi-experimental design, specific quality of care indicators were appraised before and after the implementation of the model. These dependent variables were also monitored on a control ward and data were collected on both wards at one pre-test and two post-test points. This paper presents a comprehensive overview of the literature and the methodology for the study. Planned change theory was used as a guiding framework for the implementation of the model and this process is described in detail.