This article describes the development of an advanced nurse practitioner (ANP) service in mental health. The ANPs worked within an existing hospital at night team based at Crosshouse Hospital, a district general hospital in Kilmarnock. Set against the agenda of Modernising Nursing Careers and Modernising Medical Careers, the article describes the professional and organisational background to the development, broad training requirements and skills set of this new team of ANPs. The role played by mental health ANPs in replacing junior psychiatric doctors in the out-of-hours period is of significant importance. In addition, these mental health ANPs covered the general wards in the hospital alongside their general ANP colleagues. The competency framework that the ANPs need to complete is discussed as well as the challenges faced in developing the service.