Inclusion is a philosophy that is based on values aiming at maximizing participation of all in society and education by minimizing exclusionary and discriminatory practices. Educational institutions are to provide learning opportunities to all learners indiscriminately and whether one has a disability or not. However, the great task of implementing inclusive education in public primary schools has not been going on without any challenge. The purpose of the study was to find out school-based factors influencing the implementation of inclusive education in public primary schools. The objective of the study was to determine school-based factors influencing the implementation of inclusive education in public primary schools in Nyamira County, Kenya. The study used descriptive survey design and targeted 4000 teachers. The study sampled 1040 teachers using simple random sampling and 5 Education Officers using purposive sampling. The study used Questionnaires to collect data from teachers, interview schedules to obtain data from the head teachers and education officers and checklist guide for recording observations made in each school visited. Quantitative data from questionnaires was analyzed using descriptive statistics and summarized into percentages using frequency units. Qualitative data from interview and observation schedules were analyzed thematically. The findings of the study were presented in tables, figures, pie charts and narratives. The study found that some teachers and even the learners had a negative attitude towards inclusive education. It also found out that teaching and resources were not properly utilized in the implementation of inclusive education. The study recommended that severe cases of special needs and/or disabilities to special settings for more specialized services. It also recommended that the government should train teachers and provide adequate resources to enable them implement inclusive education appropriately.