Aim: We aimed to illustrate and compare the processes of mental health policies aiming at a service delivery shift from the hospital to the community using implementation science, and to identify important implementation strategies. Methods: This study had a comparative case study design. The cases were the Belgian mental health reform, and the person-centered model of mental health in Hong Kong, China. Several documentary sources were reviewed, including the published literature and websites. Data on policy processes were extracted, analyzed using directed content analysis, and categorized into constructs of the conceptual model for evidence-informed policy formulation and implementation arranged for the mental health policy. Results: Several similarities were identified in the strategies for active implementation and dissemination; official staff allocation, and training to the community psychiatric services, an approach to adjust the number of psychiatric hospital beds, and promoting collaboration between health care sectors and social welfare sectors. Under distinct social contexts, differences were found in all processes. Conclusions: Each of the described policy processes can serve as a model for countries in similar social contexts seeking to shift their psychiatric service delivery. Furthermore, our findings suggest widely applicable implementation strategies for policies aiming at a service delivery shift.