Background The large treatment gap for mental disorders in India underlines the need for integration of mental health in primary care. Aims To operationalise the delivery of the World Health Organization Mental Health Gap Action Plan interventions for priority mental disorders and to design an integrated mental healthcare plan (MHCP) comprising packages of care for primary healthcare in one district. Method Mixed methods were used including theory of change workshops, qualitative research to develop the MHCP and piloting of specific packages of care in a single facility. Results The MHCP comprises three enabling packages: programme management, capacity building and community mobilisation; and four service delivery packages: awareness for mental disorders, identification, treatment and recovery. Challenges were encountered in training primary care workers to improve identification and treatment. Conclusions There are a number of challenges to integrating mental health into primary care, which can be addressed through the injection of new resources and collaborative care models.