BACKGROUND: In South Africa, the escalating prevalence of chronic illness and its high comorbidity with mental disorders bring to the fore the need for integrating mental health into chronic care at district level. AIMS: To develop a district mental healthcare plan (MHCP) in South Africa that integrates mental healthcare for depression, alcohol use disorders and schizophrenia into chronic care. METHOD: Mixed methods using a situation analysis, qualitative key informant interviews, theory of change workshops and piloting of the plan in one health facility informed the development of the MHCP. RESULTS: Collaborative care packages for the three conditions were developed to enable integration at the organisational, facility and community levels, supported by a human resource mix and implementation tools. Potential barriers to the feasibility of implementation at scale were identified. CONCLUSIONS: The plan leverages resources and systems availed by the emerging chronic care service delivery platform for the integration of mental health. This strengthens the potential for future scale up.