The study sought to assess factors affecting implementation of Integrated Financial Management Information System (IFMIS) in County Governments in Kenya. On focus was how staff resistance, and capacity and skills of IFMIS users affected IFMIS implementation. The study took place in Nyandarua County. The study employed descriptive survey research design. The target population constituted 70 employees. The study adopted census design. Structured questionnaires were used for data collection. The Statistical Package for Social Sciences tool aided in data analysis. Both descriptive and inferential statistics were employed in data analysis. The findings were presented in form of statistical tables. The study revealed that there exists a strong, negative and statistically significant relationship between staff resistance and IFMIS implementation; and that there exists a strong, positive and statistically significant relationship between capacity and skills of IFMIS users and its implementation. It was inferred that there is uncertainty on whether county government had instituted strategies to minimize resistance to change. The study recommended that county government should uphold the strategic plan that identifies all the constraints that derail implementation of IFMIS. The study further recommended that county government should focus on reinforcing capacity in the IFMIS project team and ensure continuity of key personnel in the system's development and implementation.