© 2020 The Author(s). Background: Social prescribing is a way of addressing the 'non-medical' needs (e.g. loneliness, debt, housing problems) that can affect people's health and well-being. Connector schemes (e.g. delivered by care navigators or link workers) have become a key component to social prescribing's delivery. Those in this role support patients by either (a) signposting them to relevant local assets (e.g. groups, organisations, charities, activities, events) or (b) taking time to assist them in identifying and prioritising their 'non-medical' needs and connecting them to relevant local assets. To understand how such connector schemes work, for whom, why and in what circumstances, we conducted a realist review. Method: A search of electronic databases was supplemented with Google alerts and reference checking to locate grey literature. In addition, we sent a Freedom of Information request to all Clinical Commissioning Groups in England to identify any further evaluations of social prescribing connector schemes. Included studies were from the UK and focused on connector schemes for adult patients (18+ years) related to primary care. Results: Our searches resulted in 118 included documents, from which data were extracted to produce context-mechanism-outcome configurations (CMOCs). These CMOCs underpinned our emerging programme theory that centred on the essential role of 'buy-in' and connections. This was refined further by turning to existing theories on (a) social capital and (b) patient activation. Conclusion: Our realist review highlights how connector roles, especially link workers, represent a vehicle for accruing social capital (e.g. trust, sense of belonging, practical support). We propose that this then gives patients the confidence, motivation, connections, knowledge and skills to manage their own well-being, thereby reducing their reliance on GPs. We also emphasise within the programme theory situations that could result in unintended consequences (e.g. increased demand on GPs).