A growing literature has indicated a relationship between social capital and certain aspects of the built environment with contributions from various disciplines, including environmental psychology, urban design, and health geography. In this systematic review and research synthesis, we summarize the literature in this domain using existing sociological and design frameworks to ascertain the effect of specific built environment domains on social capital. Our review shows that there is a significant relationship between social capital and the built environment, specifically between social cohesion and access to destinations/walkability. Positive relationships exist between social capital, design, and diversity, whereas the effect of population density on social capital is negative and unclear. We find significant methodological limitations and gaps in the published literature, including the absence of longitudinal studies and the use of a plethora of social capital and built environment measures.