A morphological and molecular study of Ornithodoros (Subparmatus) viguerasi (Acari: Argasidae) was carried out. Free-living males and females of this tick species were collected in Calcehtok cavern, Yucatán, Mexico. The morphology of the females of O. viguerasi was identical to the holotype female from Cuba. The only difference was related to size; females from Mexico were bigger than the holotype female. The male of O. viguerasi was described for the first time from the specimens collected in Mexico. The diagnostic characters are a combination of a genital aperture covered by a semicircular flap, a central sclerotized plate posterior to genital aperture, a transverse and thin plate anterior to the genital aperture located at the level of the anterior margin of coxae I, a pair of sclerotized plates bordering coxae II, III and IV, basis capituli rectangular in shape and protrusible, a hypostome roughly blunt at the apex with small denticles (it appears to be functionless), and article I of the palpi with a medial integumental extension which has a long setae on the medial margin. A comparative morphological analysis of the male described in this work with the paratype specimens from Cuba was also conducted; we conclude that the nymphs described in the original description of O. viguerasi correspond to males. Sequences of the mitochondrial 16S rDNA gene of both male and female ticks from Mexico were identical. In a phylogenetic analysis, the monophyly of the subgenus Subparmatus could not be resolved.