Marsdenia R.Br. represents the largest group of Asclepiadoideae in New Caledonia. With five new endemic species described here, and one new combination, the number of Marsdenia species increases to 18 for New Caledonia. The new species are all restricted to ultramafic substrates. Marsdenia kaalensis Meve, Gâteblé & Liede, sp. nov. is only known from the Mt. Kaala area in northwestern Grande-Terre, and M. weberlingiana Liede, sp. nov. is restricted to one locality at Hô (Houaïlou). In contrast, the other three species (Marsdenia mackeeorum Meve, Gâteblé & Liede, sp. nov., M. neocaledonica Meve, Gâteblé & Liede, sp. nov. and M. paulforsteri Meve, Gâteblé & Liede, sp. nov.) are fairly widely distributed and locally common. All new species are fully illustrated, and a distribution map is provided. Moreover, the new combination Marsdenia guillauminiana (P.T.Li) Meve, Gâteblé & Liede, comb. nov. (based on Tylophora guillauminiana P.T.Li) is proposed for this rare endemic, originally described as Tylophora micrantha Guillaumin. Tylophora anisotomoides Schltr., syn. nov., instead, is proposed as a new and additional synonym of Vincetoxicum biglandulosum (Endl.) Kunze.