Globally, the burden of non-communicable diseases (NCDs) falls disproportionately on underserved populations. Migrants and refugees are particularly vulnerable due to economic instability and systemic poverty. Despite the myriad of health risks faced by migrants and refugees, access to appropriate healthcare is hindered by structural, cultural and socioeconomic barriers. We conducted a systematic review and meta-ethnography to obtain critical insight into how the interplay of social capital and structural factors (eg, state policies and socioeconomic disadvantage) influences the prevention and treatment of NCDs in migrant and refugee populations. We included 26 studies of 14 794 identified articles, which reported qualitative findings on the structure and functions of social capital in NCD prevention and management among migrants and refugees. We synthesised findings, using the process outlined by Noblit and Hare, which indicated that migrants and refugees experienced weakened social networks in postmigration settings. They faced multiple barriers in healthcare access and difficulty navigating healthcare systems perceived as complex. Family as the core of social capital appeared of mixed value in their NCD prevention and management, interacting with cultural dissonance and economic stress. Community organisations were integral in brokering healthcare access, especially for information diffusion and logistics. Healthcare providers, especially general practitioners, were important bridges providing service-user education and ensuring a full continuum of quality care. While social capital reduced immediate barriers in healthcare access for NCD prevention and management, it was insufficient to address structural barriers. System-level interventions appear necessary to achieve equitable healthcare access in host countries. PROSPERO registration number: CCRD42020167846.