Kaptai National Park (KNP) is a protected area and represents a tropical semi-evergreen hill forest and home of widest variety of biodiversity in the country. Floristic composition and regeneration status of Kaptai National Park was assessed through stratified random sampling method. A total of 200 sample plots were taken of 20 m * 20 m in size for trees and 2m * 2 m in size for regeneration data collection. Result of the study showed that there were 114 tree species belonging to 42 families and 77 regenerating species belonging to 35 families were recorded from the sample plots. The highest tree stem and regenerating seedlings density was found 373 stem ha^-1 and 11788 stem ha^-1 for Aporosa dioica. The study indicated that A. dioica is the most dominant tree species and its natural regeneration was also abundant in Kaptai National Park. On the other hand, Shannon-Wiener’s diversity index, Margalef’s diversity index, Simpson’s and Pielou’s diversity index were recorded for all the tree species. The percentage distribution of seedlings was maximum (56.56%) in 0-50 cm height range for all species. The number of seedlings reduced proportionately with height growth indicating a reduction of recruitment to next growth stage. Among the regenerating species, Grewia nervosa showed maximum (9.15%) seedling recruitment. The study is made baseline information on the natural regeneration of tree species diversity in the protected area which is helpful to future research work on plant population change, conservation and sustainable management planning for Kaptai National Park.