Administrative decentralization is widely recognized as a governance mechanism to enhance local service delivery and social development outcomes. However, empirical evidence on its disaggregated impact in rapidly urbanizing contexts like Wakiso District, Uganda, remains limited. This study investigated the distinct effects of three constructs of administrative decentralization local staffing and management capacity, delegation of planning and implementation powers, and administrative process efficiency on three dimensions of social development: access to education, access to healthcare, and access to clean water and sanitation. A cross-sectional survey design was employed, collecting primary data from a stratified random sample of 326 respondents, including local government officials, political leaders, and community members, between May and July 2025. Data were analyzed using descriptive statistics, Pearson correlation, and simple linear regression in SPSS version 25. Results revealed significant positive relationships for all hypothesized paths: staffing capacity predicted education access (β = .68, p < .001, R² = .462), delegation of powers predicted healthcare access (β = .65, p < .001, R² = .423), and administrative efficiency predicted water and sanitation access (β = .70, p < .001, R² = .490). The study concludes that administrative decentralization is a multidimensional driver of social development and recommends targeted capacity-building, enhanced local autonomy, and streamlined administrative systems to improve service delivery outcomes.