During a survey of termite-associated nematodes in southern Taiwan (Kenting National Park), two species of Poikilolaimus, Poikilolaimus cf. floridensis and an undescribed species, were isolated from termites in the family Kalotermitidae. The undescribed species is morphologically observed, described and figured herein as P. carsiops n. sp. The new species is characterised by an unusual cross-shaped stomatal opening formed by two well developed dorsal and two subventral lip sectors, each with a triangular flap and two vestigial lateral lip sectors lacking a flap, and several other morphological characters. Based upon morphology and molecular phylogenetic analysis, P. carsiops n. sp. is closest to P. floridensis; i. e., these two species share a plesiomorphic regular cuticle and short tail in both males and females, and a lack of metastegostomatal teeth or denticle. In the molecular phylogenetic analysis, P. carsiops n. sp. and P. floridensis formed a well-supported clade which was clearly separated from, but monophyletic with, a clade that includes the other Poikilolaimus species. Because both P. carsiops n. sp. and P. floridensis have been isolated only from the kalotermitid termites, the P. floridensis/P. carsiops n. sp. clade is considered to be specialised with dry wood and damp wood termites (Kalotermitidae).