A taxonomic study on the genus Macrosemia from Vietnam in which a new species Macrosemia sapaensis sp. nov. is described. This species was collected from Lao Cai province in north Vietnam. Information on the distribution, photos of an adult, and illustrations of the male genitalia are provided for the new species. Based on the male characteristics, we provide a key to the genus Macrosemia Kato, 1925 (Hemiptera: Cicadidae) of Vietnam.