Pinnixa arenicola is redescribed and illustrated on the basis of new collections and reexamined type material. Its occurrence in the burrows of Upogebia vasquezi Ngoc-Ho is reported, along with range extensions that include Florida, Puerto Rico, Aruba, and the Cayman Islands. New collections represent the first reports of P. arenicola since original discoveries in Curaçao and suggest a potentially wide distribution of the species in the tropical western Atlantic. Following publication of the unillustrated original description for the holotype male, females were also noted to occur in Curaçao, but illustrations with limited detail were provided by Rathbun for only the male holotype specimen. Prior to our work, no illustrations have depicted female morphology, unique male gonopods, or some pereopod features of potential value in defining phylogenetic relationships.