Gelsemiaceae consist of two intercontinental disjunct genera: Gelsemium (3 species) and Mostuea (9 species). Gelsemium is distributed in eastern Asia and eastern North America, while Mostuea is disjunct between South America and Africa. In this study, sequences of three chloroplast genes (ndhF, rbcL, and matK) and the external transcribed spacer (ETS) of the ribosomal DNA region were used to examine phylogenetic relationships of Gelsemiaceae. Our results support the monophyly of Gelsemiaceae, Mostuea, and Gelsemium; however, more data are needed to resolve relationships of Gelsemiaceae with other families of Gentianales. Within Mostuea, M. surinamensis of South America is sister to the clade containing African species, indicating that it is unlikely that M. surinamensis is an introduced species from Africa since the morphology of the species is also different from all of the African species. North American species of Gelsemium form a clade that is sister to G. elegans of eastern Asia, which is consistent with flower and fruit morphology. Both Mostuea and Gelsemium show the most common phylogenetic patterns of intercontinental disjunct genera: reciprocal monophyly of species on separate continents.