Abstract: The purpose of this study was to assess the determinants of social and economic development of internally displaced persons in Rongai Sub-County in Nakuru County, Kenya. The study was guided by Community development Theory. The study adopted the descriptive research design. The target population of this was 1200 IDPs and 17 chiefs. Data was collected from respondents using questionnaires and interview guide. Quantitative data was analyzed using statistical techniques with the help of Statistical Package for Social Sciences (SPSS). Qualitative data was grouped; coded and categorized picking on cross-cutting issues and then compiled, analyzed, and interpreted. From the findings marital status; social interaction, collective action employment status, age, religion, marital status, income and sex/gender were the determinants of social and economic development of IDPs in Rongai Sub- County. This study concluded that, determinants of social and economic development in Rongai Sub-County manifested at different levels; household level, internally displaced persons and community level factors. Recommendations are that Kenya government institute a policy that guides internally displaced persons contribution to socioeconomic development, revise internally displaced persons management policies to accommodate internally displaced persons settlement and integration. Kenya government in partnership with UNHCR should ensure all displaced persons in the camps are well provided with social amenities including setting up adequate classrooms, teachers, and education facilities and adequate hospitals, equipment and healthcare workers as provided in the local and international laws. 

Keywords: Socio-economic development, internally displaced persons, law and order, employment status