Projects remain the instruments of choice for policymakers in national and international development. In Africa and other third world countries, development projects play a great role in providing basic social services. The main focus of this study was to access effects of monitoring and evaluation on successful implementation of projects in non-governmental organizations of Kajiado County. The study covered a population is 110 employees and used stratified random sampling where 50% of the entire target population formed the sample size 55) of the study. Data was collected from both primary and secondary sources using questionnaires. The findings were presented using graphs, pie charts and table diagrams respectively depending on the techniques. Based on the study findings, monitoring and evaluation 95% said it affects successful implementation of projects in non-governmental organizations of Kajiado County while 5% disagreed, on staff training 88% said it affects successful implementation of projects in non-governmental organizations of Kajiado County while 12% disagreed, The researcher recommends that monitoring and evaluation of project since it is very essential in improving performance, is also very complex, multidisciplinary and skill intensive processes. In relation to staff training the nongovernmental organizations should be able to improve the competency of personnel. It was highly recommended that monitoring and evaluation of project since it is very essential in improving performance, is also very complex, multidisciplinary and skill intensive processes.