Marsdenia magallanesiana Juárez-Jaimes, a new species from the state of Jalisco, Mexico, is described and illustrated here; it is compared with M. edulis S. Watson and M. callosa Juárez-Jaimes & W. D. Stevens, which are the morphologically most similar species to it. The three species grow in separate areas of the tropical deciduous forest of the Pacific slopes of Mexico. However, the new species is distinguished by the absence of a fleshy callus on the corolla sinus lobes, its corona lobes suborbicular with margins not thickened, and its style appendage subconic with a short, slightly divided apex.