A systematic survey was conducted to assess the diversity of herpetofauna in the Mahausakande regenerating tropical rainforest (MRF) in Kiriella, Sri Lanka. Approximately 900 man hours were spent in the field over a period of four months to document amphibians and reptiles in representative habitat types, using different sampling methods. A total of 21 species of amphibians and 45 species of reptiles were recorded from MRF, of which 15 amphibians and 26 reptile species are endemic. The reptiles include 24 species of snakes, and 21 species of tetrapod reptiles. Among the endemics were three amphibian genera and six reptile genera. Two specimens of burrowing snakes (Typhlops sp.) collected may be new to science, and these will be further examined in the future. The most common species observed in MRF include the Common Paddy Field Frog (Zakerana syhadrensis), Zara’s Hump-nosed Viper (Hypnale zara), and the Kangaroo Lizard (Otocryptis wiegmanni). Of the total herpetofaunal species recorded in MRF, 11 species (16%) are considered as nationally threatened. The survey recognized several species of amphibians and reptiles that could be used as important ecological indicators to monitor the quality of habitats in the Mahausakande regenerating forest. The findings of the survey resulted in a two-fold increase in the herpetofaunal species recorded in MRF. The data gathered from the survey was also used for upgrading the IUCN National Red List.