Performance of students is a product of socio-economic, psychological and environmental factors. This study aimed at finding out factors that contribute to poor performance in Kenya Certificate of Primary Education examination in public day primary schools in Mwimbi Division, Maara District, Kenya. The study realized the following as factors contributing to poor performance in primary national examination; inadequate learning resources, inadequate monitoring by head teachers, understaffing, high teacher turnover rate, inadequate prior preparation, lack of motivation for teachers, large workload, absenteeism by both teachers and pupils, pupils lateness, lack of support from parents. The following recommendations were made; more teachers to be employed to reduce workload, Ministry of Education to organize induction courses for head teachers to equip them with managerial skills, parents to be educated on the importance of basic education for their children, mode of rewarding teachers to be established. The study is expected to give insight reference to policy makers, scholars and researchers in order to improve the weak areas.