Health workers are pivotal for non-communicable disease (NCD) service delivery, yet often are unavailable in low- and middle-income countries (LMICs). There is limited evidence on what NCD-related tasks non-physician health workers (NPHWs) can perform and their effectiveness. This study aims to understand how task-sharing is used to improve NCD prevention and control in LMICs. We also explored barriers, facilitators, and unexpected consequences of task-sharing. Databases searched in two phases and included MEDLINE, EMBASE, CENTRAL, CINAHL, Cochrane, and clinical trial registries, and references of included studies from inception until 31st July 2024. We included randomised control trials (RCTs), cluster RCTs, and associated process evaluation and cost effectiveness studies. The risk of bias was assessed using the Cochrane Risk of Bias Tool v2. PROSPERO: CRD42022315701. The study found 5527 citations, 427 full texts were screened and 149 studies (total population sample>432567) from 31 countries were included. Most studies were on tasks shared with nurses (n=83) and community health workers (n=65). Most studies focussed on cardiovascular disease (n=47), mental health (n=48), diabetes (n=27), cancer (n=20), and respiratory diseases (n=10). Seventeen studies included two or more conditions. Eighty-one percent (n=120) of studies reported at least one positive primary outcome, while 19 studies reported neutral results, one reported a negative result, eight (5.4%) reported mixed positive and neutral results, and one reported neutral and negative findings. Economic analyses indicated that task-sharing reduced total healthcare costs. Task-sharing is an effective intervention for NCDs in LMICs. It is essential to enhance the competencies and training of NPHWs, provide resources to augment their capabilities, and formalise their role in the health system and community. Optimising task-sharing for NCDs requires a holistic approach that strengthens health systems while supporting NPHWs in effectively addressing the diverse needs of their communities. Registration: PROSPERO CRD42022315701.