A new species of Teinostoma (Tornidae) is described from an under-investigated section of the anchialine cave system Cenote Crustacea, situated on the northeastern coast of the Yucatán Peninsula. Teinostoma brankovitsi n. sp. is the first anchialine gastropod reported from the Yucatán Peninsula and the first record of the family from an anchialine cave. Specimens were found in chalky sediments riddled with orange bacterial patches, c. 450 m from the inland entrance pool, in complete darkness. Teinostoma brankovitsi has a circular, multispiral operculum with a central nucleus and does not have tentacles on the foot or opercular lobe. Specimens possess a taenioglossate radula with a central tooth broadly V-shaped and a serrated cutting area with two basal denticles. The diagnosis of Teinostoma is emended based on these new findings.