Political decentralization is theorized to enhance social development by improving governance responsiveness, yet empirical evidence at the sub-county level in Uganda remains mixed. This study investigated the disaggregated impact of three political decentralization constructs citizen participation, local accountability, and decision-making transparency on three core social development outcomes: access to education, healthcare, and clean water. A crosssectional survey design was employed, collecting primary data from a stratified random sample of 212 local government officials and political leaders in Wakiso District between May and July 2025. Data were analysed using descriptive statistics, Pearson correlation, and simple linear regression in SPSS. Results revealed significant positive relationships for all hypothesized paths: citizen participation predicted access to education (β = .65, p < .001, R² = .423); local accountability predicted access to healthcare (β = .61, p < .001, R² = .372); and transparency predicted access to water and sanitation (β = .68, p < .001, R² = .462). The study concludes that the specific mechanisms of political decentralization are distinct and powerful drivers of discrete social development outcomes. It recommends tailored governance reforms that strengthen participatory forums, accountability channels, and transparent decisionmaking processes to improve local service delivery.