The alpheid shrimp Nennalpheus Banner & Banner, 1981, hitherto known only from a few records in the tropical western Pacific, is recorded for the first time from the tropical eastern Atlantic, as well as from the Indian Ocean. Nennalpheus gabonensis sp. nov. is described based on a single but complete male specimen collected in mediocre visibility conditions at 11 m depth on a rocky reef north of Libreville, Gabon. The new species presents a substantial number of morphological differences from the two other species of Nennalpheus, especially in the armature of the cheliped fingers. The previously known distribution range of Nennalpheus sibogae (De Man, 1910), the type species of the genus, is extended significantly to include the Central Pacific (Hawaiian Archipelago) and the Indian Ocean (Glorioso Islands in the Scattered Islands group, and Mayotte Island in the Comoro Archipelago). In addition, new illustrations of N. sibogae are provided, including the previously not figured mouthparts and high-quality, contrasting background colour photographs. Field observations indicate that Nennalpheus is able to produce a weak snapping sound by rapidly closing one or both chelipeds, a previously suspected, but never observed behaviour.