Background: Nursing care models provide the infrastructure for organizing and delivering care to patients and families. Over the decades, different models have waxed and waned. Since the 1980s, the primary nursing model has gained increasing prominence. However, there is no systematic research evidence on the effects of this model for patients, their family members, nursing staff or the care organization. This subject has much current relevance because of the requirement to develop evidence-based nursing care. Objective: To describe the effects of the primary nursing model for patients, their family members, nursing staff and the care organization. Design: A systematic literature review. The studies selected for review (n=9) were appraised for quality using the Quality Assessment Tool for Quantitative Studies, as developed by the Effective Public Health Practice Project. Data sources: The research data were collected from four databases from January 1990 to March 2013. Results: Research on the effects of the primary nursing model has largely been restricted to the effects for patients and nursing staff. No data are available on how it affects the patient's family members or the care organization. The preliminary evidence suggests that the primary nursing model may have beneficial effects for patients in the context of maternity care. There is less evidence of the primary nursing model's positive effects for nursing staff. However, it is possible that the model contributes to an increased sense of job control and autonomy. Conclusion: The existing body of research has methodological shortcomings, and more RCT studies are needed to establish the effects of the primary nursing model, for instance on the organization's costs, nurses' job satisfaction and staff retention. Further research is also needed into the effects of the primary nursing model on numerically measurable outcomes, such as medication errors during hospital care and the length of treatment periods.