Background and Objective: Low-and-middle-income countries (LMICs) are experiencing growing demand for non-communicable disease and mental health healthcare services yet face a persistent shortage in access to specialist health workers (SHWs) in these services. Task shifting is an approach used to address this gap in service provision in which specific healthcare tasks are shifted to larger cadres of non-specialist health workers, including lay health workers (NSHWs) with SHWs potentially taking on supervisory roles. Previous evaluative studies have demonstrated that task shifting is both clinically and economically effective, however the impact of task shifting on NSHWs is not fully understood. This information is important given health workers are a key resource in addressing the growing gap in healthcare provision in LMICs. Understanding what challenges and benefits health workers encounter when engaging in task shifting will contribute to accommodating their likely support needs when implementing future task shifting initiatives. Using a feasibility trial evaluating the effectiveness of a brief talking therapy for depression as an exemplar, the aim of this study is to explore how diabetic health workers in publicly funded diabetic healthcare services in Bangladesh and Pakistan experience delivering a mental health intervention for patients with diabetes and depression multimorbidity. Methods: Using grounded theory methodology, we will make field observations and interview diabetic health workers trained in delivering culturally adapted behavioural activation about their experiences of integrating mental healthcare into their usual practice. Recruitment to the study will begin in December 2022 and continue until theoretical saturation is reached. Results: We will present preliminary Findings contributing towards the development of an explanatory theory about how mental health task shifting impacts on diabetic health workers in Bangladesh and Pakistan.