This study was about establishing factors affecting level of K.C.S.E. performance in Kitui District. The major purpose was to determine the factors and their influence on K.C.S.E. performance. The overall and long-term aim of this study was to contribute to the improvement of K.C.S.E. performance of students of Kenya. It is also expected to contribute information that could be useful in designing possible ways of improving the performance in the district. Secondly, to establish whether availability of learning facilities and the teachers have any effect on performance in KCSE performance. Thirdly, to find out the role of administration on students performance. In addition to find out the effect of class size and management of homework on students performance in K.C.S.E. Examination in Kitui District. The setting for this study was ten public secondary schools in Kitui district. The method for this study was survey design because it covers large population and determined current status of population with respect to more variables. To get the samples the researcher used stratified random sampling.