BACKGROUND: Non-communicable diseases (NCDs) are projected to become the leading cause of disability and mortality in sub-Saharan Africa by 2030; a vast treatment gap exists. There is a dearth of knowledge on developing evidence-based interventions that address comorbid NCDs using a task-shifting approach. The Friendship Bench, a brief psychological intervention for common mental disorders delivered by trained community grandmothers, is a promising intervention for comorbid NCDs. Although task-shifting appears to be a rational approach, evidence suggests that it may bring about tension between existing professionals from whom tasks are shifted. A Theory of Change approach is an effective way of managing the unintended tension by bringing together different stakeholders involved to build consensus on how to task shift appropriately to the parties involved. We aimed to use a theory of change approach to formulating a road map on how to successfully integrate diabetes and hypertension care into the existing Friendship Bench in order to come up with an integrated care package for depression, hypertension and diabetes aimed at strengthening NCD care in primary health care systems in Zimbabwe. METHOD: A theory of change workshop with 18 stakeholders from diverse backgrounds was carried out in February 2020. Participants included grandmothers working on the Friendship Bench project (n = 4), policymakers from the ministry of health (n = 2), people with lived experience for the three NCDs (n = 4), health care workers (n = 2), and traditional healers (n = 2). Findings from earlier work (situational analysis, desk review, FGDs and clinic-based surveys) on the three NCDs were shared before starting the ToC. A facilitator with previous experience running ToCs led the workshop and facilitated the co-production of the ToC map. Through an iterative process, consensus between the 18 stakeholders was reached, and a causal pathway leading to developing a framework for an intervention was formulated. RESULTS: The ToC singled out the need to use expert clients (people with lived experience) to promote a patient-centred care approach that would leverage the existing Friendship Bench approach. In the face of COVID-19, the stakeholders further endorsed the use of existing digital platforms, notably WhatsApp, as an alternative way to reach out to clients and provide support. Leveraging existing community support groups as an entry point for people in need of NCD care was highlighted as a win-win by all stakeholders. A final framework for an NCD care package supported by Friendship Bench was presented to policymakers and accepted to be piloted in five geographical areas. CONCLUSIONS: The ToC can be used to build consensus on how best to use using an existing intervention for common mental disorders to integrate care for diabetes and hypertension. There is a need to evaluate this new intervention through an adequately powered study.