A new species of Synalpheus from Punta Mita, Nayarit, Mexico, is described. The new species was collected from coral rubble at a depth of 3 m. Synalpheus lani is morphologically similar to S. superus Abele & Kim, 1989, S. sanjosei Coutière, 1909, and S. townsendi mexicanus Coutière, 1909, but can be distinguished by a more elongated major chela without a spine on the dorsodistal margin of the merus. The length/width ratios of merus, propodus, and dactyl of the third pereopod also separate the four species. From this group of similar species, the new species has been recorded sympatrically only with S. sanjosei.