A new species of Melloina Brignoli, 1985, Melloina santuario sp. nov., is described from a cave in Venezuela. This is the third species described in this rarely sampled genus, and the first species known from both male and female. The male of M. santuario sp. nov. is distinguished by a longer embolus and fewer number of spines on the anterior tarsi. Females and immatures are distinguished by having fewer numbers of labial cuspules. The description of a new species from male and female samples increases our knowledge about Melloina. This added knowledge is important to the understanding of mygalomorph relationships, mainly in the Theraphosoidina, as Melloina is a basal genus within the Paratropididae.