This study examines the relationship between residential environmental satisfaction, social capital, and place attachment. Previous studies on place attachment and residential environments have not fully considered the components of residential environments or executed an integrated analysis. This study includes diverse aspects of residential environmental satisfaction such as accessibility, comfort, and safety, which permits a comparison of the influence of each element. Furthermore, this study examined the mediating effect of social capital between residential environments and place attachment. Online surveys were conducted with 750 residents in the metropolitan city of Seoul, Korea, and mediation regression analysis as employed. The results indicated that residential environmental satisfaction had a positive effect on place attachment. In particular, accessibility had the greatest effect on place attachment. Furthermore, social capital had a mediating effect on all sub-components of residential environments. Today, many countries, including China and India, pursue and experience rapid urbanization much like Seoul, which has undergone it over several decades. However, this causes a variety of urban problems that might hinder long-term sustainable development. Therefore, this study suggests that the importance of qualitative development for sustainability should be recognized and incorporated together with quantitative development.