In Kenya, County Governments are mandated to carry out development projects anchored on their County Integrated Development Plans (CIDPs). The implementations of these projects have been met by higher number of failures. However, irrespective of the outcome of the projects, the aspect of Monitoring and Evaluation (M&E) is rarely cited in relation to the outcome. The objectives of conducting Evaluations is to determine the relevance and realization of project objectives, efficiency and effectiveness levels of the project, impact and sustainability as well as to haul along the lessons learnt; these together, helps in decision making. This study sought to determine the influence of monitoring and evaluation adoption on implementation of county government sponsored projects in Rabai sub-county. Specifically, the study investigated the influence of top management support, M&E planning, budget allocations for M&E, and community involvement on implementation of county government sponsored projects in Rabai sub-county. The study employed descriptive survey research design and had a target population of 46 county governments sponsored projects in Rabai sub-county from which the accessible population comprised 92 project officials were derived. The study used pre-tested questionnaires for data collection. Descriptive, correlation, and inferential data analysis were carried out and results presented in form of table and figures. The findings revealed that the top management support for M&E had no significant influence on implementation of county government sponsored projects. It was also revealed that top management gave very minimal supports to carrying out capacity assessment for firms bidding for M&E and that M&E planning, adequate Budget allocations for M&E, and facilitating Community involvement in M&E leads to a rise in implementation of county government sponsored projects in Rabai Sub-County. The study concluded that there is need to improve M&E processes. The study recommended for top management support for M&E adoption, by actively carrying out capacity assessment for firms bidding for M&E, and ensuring that the firms selected for M&E are committed to top deliverables.