The herpetofauna of southern Philippines, especially Davao Region, though remarkable, remains the least studied, most especially in karst ecosystems like caves and subterranean habitats. To address this gap, we conducted the first herpetological survey of Samal Island, a small karst island in the Davao Region, and the first survey of any karst ecosystem in the area. Opportunistic sampling was carried out in 30 caves on the island, 17 of which yielded herpetofauna records either inside the cave or in its immediate vicinity. We documented 24 species (eight amphibians and 16 reptiles), including two potentially new species: Platymantis sp. and Cyrtodactylus sp. Of the 22 identified species, three are new records for Davao Region (Kaloula picta, Brachymeles pathfinderi, and Bronchocela cf. cristatella). Our survey recorded seven Mindanao endemics, five Philippine endemics, and ten native or non-endemic species. The discovery of potential new species, new island records, and expanded distribution records highlights the urgent need for comprehensive herpetofaunal surveys in the southern Philippines, particularly in overlooked habitats such as caves and karst landscapes, which serve as critical refugia for karst-associated species.