The main objective of this study was assessing the species diversity and plant community structure of Nandi forests of Kenya. Seventy six (20 × 20 m) sample plots, of which 27 located in North Nandi and 49 from South Nandi Forest were used to collect vegetation data. Sample plots were established along transects measuring 1.0 to 1.6 km length and adjacent transects were 500 m apart from each other. Abundance data of species was used for species diversity, similarity, species richness estimation and plant community analysis. PC-ORD, CANOCO and Estimates were used to analyze the data. A total of 321 species belonging to 243 genera and 92 families were identified in this study. Out of these, 253 species were recorded in South Nandi and 181 in North Nandi. South Nandi Forest had higher species diversity than that of North Nandi Forest. Three distinct plant communities including; Diospyros abyssinica-Heinsenia diervilleoides, Trilepisium madagascariense-Solanum mauritianum and Turraea holstii - Ehretia cymosa were identified.