This study evaluated the effect of training as a capacity building practice on performance of County Assemblies in Kenya. Descriptive research design was deployed. The targeted population was 135 respondents that comprised of members of the county assembly both elected and nominated, administrative staff, speaker of the county assembly, deputy speaker and both majority and minority leaders in Kericho County Assembly. Given that the target population was relatively small (135), the study used census approach to include all members of the population. Furthermore, the on-going study employed secondary and also of data collection tools, a pilot test was carried out. Moreover, qualitative data was analyzed by the use of thematic analysis and findings presented in narrative form. Descriptive as well as inferential statistics was employed to analyze quantitative data with the assistance of SPSS. Moreover, descriptive statistics encompassed frequency distribution, standard deviation, mean and percentages. In this study, inferential statistics included multivariate regression analysis and Pearson correlation analysis. The study findings were given in figures and tables. The study found that training was conducted through workshop and conference which assisted in acquisition of skills. Seminars as well as short-term courses were sponsored by the county, training therefore had a significant influence that was positive on the way the County Assembly performed (P<0.05). The study concluded that training had a significant influence that was positive on the performance of Kericho County Assembly. The study suggested that sponsorship programs should be increased and more sensitization campaign to enable equal opportunity to improve skills. Also knowledge management should be practice.