["Corporate Social Responsibility and Environmental Management, EarlyView. ", "\nABSTRACT\nThis study critically examines the role of relational capital (RC) in shaping the sustainable development of small and medium‐sized enterprises (SMEs). Although RC is widely recognised as a strategic resource, existing evidence remains fragmented, context‐dependent and theoretically underdeveloped. Adopting a systematic literature review guided by the PRISMA protocol, the study analyses 77 articles published between 2012 and 2021 across 39 academic journals, with particular attention to underexplored contexts, such as the Middle East and North Africa (MENA) region. The findings reveal that RC does not exert a uniform effect on sustainability outcomes; rather, its influence is indirect and contingent, operating through mechanisms such as knowledge sharing and innovation that vary across institutional and organisational settings. This heterogeneity limits the generalisability of prior findings and constrains the development of actionable insights. The study reconceptualises RC as a contextually embedded and strategically deployed capability, highlighting the need for integrative and context‐sensitive approaches. It proposes a research agenda that emphasises underrepresented regions, longitudinal designs and mixed‐methods approaches to better capture the dynamic and multi‐dimensional nature of RC, thereby advancing both theory and practise within the sustainability domain.\n"]