The role of nurses in primary care is understudied. The purpose of this study was to describe the current registered nurse (RN) role in three Primary Care Networks (PCNs) in western Canada and to identify opportunities for optimal utilization of RNs in these settings. Case study methodology included interviews and document review. Although the RN role evolved during the study, most RNs focused on chronic disease management. Role ambiguity was evident between nurses and with interprofessional team members. Relationships of RNs to other providers, particularly physicians, impacted the enactment of the nursing role. Other barriers to role enactment included physician fee-for-service remuneration, management structures and processes, lack of access to electronic medical records and lack of previous opportunities to apply primary health-care education in the practice setting. Further work is needed to optimize the RN role in primary care to ensure maximum impact for patients, providers and the health system overall.