Projects implementation remain to be universal in all entities of life more so the policy makers with respect to both local and international development, but then ironically, the poor performance of projects and the disappointment of projects appear to be a commonest scenario. The main purpose of this study was to determine factors affecting successful implementation of projects in non-governmental organizations of Kajiado County. Specific objectives were to find out the effects of staff training, project management on successful implementation of projects in non-governmental organizations of Kajiado County. The study adopted descriptive research design. 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. Study findings, revealed that staff training affect successful implementation of projects in non-governmental organizations of Kajiado County. The researcher recommends that the firm allocate enough money for staff training the non-governmental organizations should be able to improve the competency of personnel. On the other hand, the study recommended efficient project management for better performance. It was highly recommended that the stakeholders should be able to make major decisions relating to the project and determine the outcome of the decisions. Finally, the study recommends monitoring and evaluation of project since it is very essential in improving performance, is also very complex, multidisciplinary and skill intensive processes.