Objectives Implementation of new knowledge into routine care is a complex endeavour. Involving employees in the change process, good planning and communication as well as a commitment to training has been highlighted as important factors for successful implementation. Acknowledging change as a process may also be helpful. The aim of this paper was to describe the initial phase of the implementation process in changing to evidence-based practisepractices within a child and adolescent mental health service. Method Prior to the five-year project, an external service evaluation was carried out. The employees expressed a need for a clear direction from management to guide their clinical practice. A vision and strategy for the service was developed. Employees participated in the process of developing clinical standards during the first phase of implementation. Results Fixsen’s four stage model and the PSDA circle were used to guide the implementation process. The employees developed a template for a clinical standard based on national and international clinical guidelines. During the period, 17 clinical standards were established and 10 new evidence-based methods were implemented. All service leads (13) and a group of senior clinicians (32) were invited to participate in an evaluation five years after the initial service evaluation. There was overall agreement that the mental health service was developing positively providing high quality services for children and adolescents. In addition, both groups agreed that the introduction of clinical standards was important in ensuring quality care. Conclusion Involving employees in the implementation process seemed to be an important factor in changing a mental health service.