Objective To assess the effectiveness of care provided by mid-level health workers. Methods Experimental and observational studies comparing mid-level health workers and higher level health workers were identified by a systematic review of the scientific literature. The quality of the evidence was assessed using Grading of Recommendations Assessment, Development and Evaluation criteria and data were analysed using Review Manager. Findings Fifty-three studies, mostly from high-income countries and conducted at tertiary care facilities, were identified. In general, there was no difference between the effectiveness of care provided by mid-level health workers in the areas of maternal and child health and communicable and noncommunicable diseases and that provided by higher level health workers. However, the rates of episiotomy and analgesia use were significantly lower in women giving birth who received care from midwives alone than in those who received care from doctors working in teams with midwives, and women were significantly more satisfied with care from midwives. Overall, the quality of the evidence was low or very low. The search also identified six observational studies, all from Africa, that compared care from clinical officers, surgical technicians or non-physician clinicians with care from doctors. Outcomes were generally similar. Conclusion No difference between the effectiveness of care provided by mid-level health workers and that provided by higher level health workers was found. However, the quality of the evidence was low. There is a need for studies with a high methodological quality, particularly in Africa - the region with the greatest shortage of health workers.