Two new species of Tetrastigma from Thailand, T. calcicola Kochaiph. & Trias-Blasi sp. nov. and T. jaichagunii C.L.Li ex Kochaiph. & Trias-Blasi sp. nov. are described and illustrated. Tetrastigma calcicola sp. nov. is a slender climber restricted to the open areas on limestone mountains at high elevation in the northern part of Thailand. The other species, T. jaichagunii sp. nov., is similar to T. harmandii Planch., but differs from it by having more densely verrucose young branches, broader leaflets, 4-lobed thick discs, bigger globose berries and oblongoid seeds. This species occurs along streams or in forest margins in evergreen forest and it is widely distributed in several parts of Thailand.