Globally, mental health systems have failed to adequately respond to the growing demands of mental health services resulting in a disparity between the need and provision of treatment. Paucity of mental health care providers contributes to the aforementioned disparity. This can be addressed by engaging Nurse Practitioners (NPs) in an integrated model within healthcare teams. This paper describes the implementation of NPs as Most Responsible Provider (MRP) care of model in a specialised mental health hospital in Ontario, Canada. Guided by the participatory, evidence-based, patient-focused process for advanced practise nursing (APN) role development, implementation, and evaluation (PEPPA) framework, authors developed a model of care and implemented the first seven steps of the PEPPA framework – (a) define the population and describe the current model of care, (b) identify stakeholders, (c) determine the need for a new model of care (d) identify priority areas and goals of improvement, (e) define the new model of care, and (f) plan and implement the NP as MRP model of care. Within these steps, different strategies were implemented: (a) revising policies and procedures (b) harmonising reporting structures, (c) developing and implementing a collaborative practise structure for NPs, (d) standardised and transparent compensation (e) performance standards and monitoring (f) Self-Assessment Competency frameworks, education, and development opportunities. This paper contributes to the state of the knowledge by implementing NPs as MRP model of care in a specialised mental health care setting in Ontario, Canada; and advocates the need for incorporating mental health programmes within the Ontario nursing curriculum.