The poeciliid Heterophallus echeagarayi (Álvarez, 1952) has been recorded in the Tonalá and Grijalva-Usumacinta basins (Mexico). However, the present delimitation of its distribution could result from the lack of specific samplings of small-bodied species in the surrounding basins with similar habitats and environmental conditions. Our aim was to review its distribution through intensive sampling in the same basin and in adjacent basins. The result was an increased record in the Grijalva-Usumacinta basin, among them in the Palizada River, and the extension of its geographical distribution to the Chumpan, Candelaria and Mamantel basins. The first reports of H. echeagarayi in these three basins update its distribution in the coastal plain of the South of the Gulf of Mexico.