This research sought to find out the influence of appropriate instructional resources on retention of pupils with disabilities in mainstreamed Primary Schools in Bomet County, Kenya. The challenge that this study sought to address was low retention of Pupils with Disabilities (PWDs) in mainstreamed schools. This study was embedded in Systems Theory by Von Bertalanffy [1]. It adopted survey research design. The target population was 840 teachers. Yamane formula was applied to get a sample size of 278 teachers. Multi-stage sampling procedure was applied. The findings of the study revealed that appropriate instructional resources significantly influenced the retention of PWDs by = 42.1% (p<0.05). The study also reports a positive and statistically significant relationship between appropriate instructional and retention of pupils with disabilities (r = 0.842; p<0.05). The study concludes that appropriate instructional resources positively and significantly influence the retention of pupils with disabilities. Therefore, when appropriate instructional resources are provided, retention of pupils with disabilities increase and conversely, in the absence of these resources, retention of pupils with disabilities will be challenging. The study recommended that appropriate instructional resources such as textbooks, supplementary curriculum support materials, learning devices or aiders including braille kits, printouts, pointers, embossers friendly to pupils with disabilities be supplied to improve their retention in mainstreamed primary schools.