South Korea has historically relied on inpatient psychiatric care. Although the 1995 Mental Health Act aimed to promote community mental health services, progress in developing community-based interventions has been limited. This review aims to provide a concise analysis of the current state of research on evaluating community mental health care in Korea, employing a comparative perspective with the United Kingdom (UK), where community-based mental health approaches have been more extensively studied and implemented. On November 19, 2024, a literature search was conducted using PubMed. The search strategy combined keywords related to mental illness and community intervention with the terms “Korea” or “United Kingdom.” The review focused on randomized controlled trials from both countries that assessed patient-level outcomes of community-based mental health interventions. The findings reveal a striking contrast: in Korea, only one randomized pilot trial focused on depression in older adults was found. In contrast, 69 studies were identified in the UK, including 13 pilot/feasibility studies and 56 main studies, with 38 of these addressing severe mental illness. This clear difference underscores the limited research and evaluation of community-based mental health interventions in Korea. The results indicate a pressing need for research to assess these interventions. Such research could guide policy reforms toward deinstitutionalization and help Korea strengthen its community-based mental health system in line with global trends.