Abstract Background Community-based programmes [CBPs], targeting increased physical activity and/or healthier eating, have been used in the prevention and management of non-communicable diseases. However, CBPs are only useful, insofar as they can be scaled up and sustained in some meaningful way. Social networks—defined as “social structures that exists between actors, individuals or organizations”—may serve as an important tool to identify underlying mechanisms that contribute to this process. This scoping review aimed to map and collate literature on the role of social network research in scaling-up and sustaining physical activity and/or diet CBPs in low-and middle-income countries [LMICs]. Methods Arksey and O’Malley’s framework and its enhancement were followed. Inclusion criteria were peer-reviewed articles exploring the role of social networks in scaled-up and/or sustained physical activity and/or diet CBPs in adult populations, published in English since 2000, and based in a LMIC. Databases searched were PubMed, Cochrane, Scopus, Web of Science, CINAHL, SocIndex, International Bibliography of the Social Sciences, and Google Scholar. Books, conference abstracts, and programmes focused on children were excluded. Two reviewers independently selected and extracted eligible studies. Included publications were thematically analysed using the Framework Approach. Results Authors identified 12 articles for inclusion, covering 13 CBPs. Most were based in Latin America, with others in the Caribbean, the Pacific Islands, Iran, and India. All articles were published since 2009. Only three used social network analysis methods (with others using qualitative methods). Five main social network themes were identified: centralisation, cliques, leaders, quality over quantity, and shared goals. Contextual factors to be considered when scaling-up programmes in LMICs were also identified. Conclusions This review has shown that the evidence of the use of social network research in programme scale-up has not yet caught up to its theoretical possibilities. Programmes aiming to scale should consider conducting social network research with identified network themes in mind to help improve the evidence-base of what network mechanisms, in what contexts, might best support the strengthening of networks in physical activity and diet programmes. Importantly, the voice of individuals and communities in these networks should not be forgotten.