This study presents the first checklist of the lesser known terrestrial biodiversity in forests over limestone karst of Calicoan Island in Guiuan Marine Reserve Protected Landscape and Seascape, Guiuan, Eastern Samar, Philippines. Plants and terrestrial vertebrate species in nine 20x20 m plots and 18 line transects were recorded and identified. A total of 60 bird, eight reptile, one amphibian, and six mammal species were recorded. Moreover, a total of 41 floral species were documented belonging to 17 plant families and 24 genera. Of the plant species recorded, 5 were shrubs and 35 were trees. This study reported a new locality record of the Philippine endemic tree species Hancea wenzeliana, and new island records for fauna such as Varanus samarensis and Cyrtodactylus sumuroi, among many others. To date, the present study is the only assessment of herpetofauna and mammals in Guiuan and represent new island records for most of these taxa in Calicoan Island. Among plants, Shorea negrosensis, Aquilaria cuminigiana and Wallaceodendron celebicum were identified to have a vulnerable conservation status based on their IUCN Red List and DENR-DAO 2017-11. These native and endemic plants can be used for reforestation programs in the area, and conserving biodiversity in general will be crucial to potential ecotourism programs.