This study examines the impact of decentralization on socio-economic development in the chiefdoms of Bo District, Sierra Leone, with particular attention to primary health care services. Following the reintroduction of decentralization in 2004 after the civil war, local councils and chiefdom administrations were expected to improve service delivery and strengthen community participation in governance. A mixed-method approach was adopted, combining quantitative survey data and structured interviews. A total of 414 respondents were selected across sixteen chiefdoms using stratified sampling techniques. Data were analyzed using SPSS, employing descriptive statistics and Pearson’s chi-square tests to assess associations between decentralization and selected health indicators, including malaria, enteric fever, labour pain-related deaths, HIV/AIDS, and anaemia. The findings reveal mixed outcomes regarding the impact of decentralization on health service delivery and socio-economic development. While decentralization has improved local participation and awareness of health-related issues, significant challenges persist in the provision, accessibility, and effectiveness of primary health care services. Inferential statistical results indicate varying degrees of association between decentralized governance structures and health outcomes within the district. The study concludes that although decentralization has created opportunities for local involvement in governance and development, institutional, financial, and administrative constraints continue to limit its full potential in enhancing socioeconomic development in the chiefdoms of Bo District.