Although neighborhood-level housing mix has been found associated with positive outcomes, much more efforts have been put to identify underlying mechanisms to explain how and why housing mix might exert impacts on individual outcomes. In recent decades, social capital has increasingly gained attention in the neighborhood effects literature. Causal pathways transpiring through housing mix to expected outcomes are also showcased for the selection of social capital as the mediating mechanism. In order to better understand the mediation role of social capital, theories of social capital from both the Sociology and the Political Science school are reviewed under the housing mix situation. In light of the synthesis of definitions, it can be concluded that social capital theorists across disciplines shared the belief that the structural construct “social networks” is a prerequisite yet with different priorities on either the cognitive or instrumental social benefits emanating from it. This chapter proceeds to distinguish and anchor specific constructs and forms from various expressions that can be reorganized as the progressive formation process of intergroup social capital.