Extending prior findings that the objective built environment (OBE) significantly influences residents’ life satisfaction (LS), this chapter aims to uncover the underlying mechanisms through which these effects occur. Specifically, it examines the mediating roles of Perceived Environmental Quality (PEQ), Perceived Safety (PES), Social Capital (SC), and Self-Rated Health (SRH) in the relationship between OBE and LS. Using a structural equation modeling (SEM) approach, the chapter first validates the measurement models for latent constructs and then tests a series of direct and indirect pathways based on proposed hypotheses. Section 9.1 presents confirmatory factor analysis, which confirms the reliability and validity of the measurement models for PEQ, SC, and LS. Section 9.2 details the structural model results, revealing significant effects of OBE factors—such as Population Density, Building Density, Functional Mix Diversity, Road Intersection Density, Bus Line Density, Bus Stop Density, POI Density—on the mediators, and subsequently on LS. Section 9.3 employs bootstrapping methods to test specific indirect effects, identifying multiple significant mediation pathways, including simple and serial mediations involving PEQ, PES, SC, and SRH. The findings demonstrate that OBE influences LS not only directly but also through intertwined perceptual and social mechanisms, highlighting the importance of mediating processes in urban well-being research. This chapter provides a nuanced understanding of how built environments shape subjective well-being, offering theoretical and practical insights for urban planning and policy-making.