Rapid urbanization has emerged as one of the most defining demographic and spatial transformations of the twenty- first century, reshaping the social, economic, and physical fabric of cities and municipalities across the developing world. In sub-Saharan Africa, urbanization has proceeded at rates far exceeding the capacity of municipal governments to provide adequate housing, sanitation, healthcare, education, and social protection services, generating significant deterioration in social welfare and living conditions for urban residents, particularly the poor. In Uganda, rapid urban growth driven by rural-urban migration, natural population increase, and administrative reclassification of peri-urban areas has placed immense pressure on municipal service delivery systems. In Nansana Municipality, Wakiso District, one of Uganda's fastest-growing urban centers, rapid urbanization had produced a complex and compounding set of social welfare and living condition challenges that demanded empirical investigation. This study examined the effects of rapid urbanization on social welfare and living conditions in Nansana Municipality. The study adopted a cross- sectional survey design integrating quantitative and qualitative approaches. A sample of 145 respondents comprising residents, municipal officials, social service providers, and community leaders was selected through stratified random sampling. Structured questionnaires and key informant interviews were used for data collection. Pearson correlation and multiple linear regression analyses were applied to examine the relationship between rapid urbanization and social welfare and living conditions. The findings revealed a strong negative and statistically significant relationship between rapid urbanization and social welfare and living conditions (r = -0.771, p < 0.05). Infrastructure overload (β = -0.452), environmental degradation (β = -0.431), and social service strain (β = -0.443) were each significant negative predictors of social welfare and living conditions. Residents in areas experiencing the most intense urbanization pressures recorded the lowest scores on housing quality, access to clean water and sanitation, healthcare access, and overall quality of life. Rapid urbanization was a significant and negative determinant of social welfare and living conditions