Diatraea postlineella , that we call the Guatemalan sugarcane borer, was described from Quirigua, Guatemala, based on one male specimen; the host was unknown. Recently, more specimens of D. postlineella from Guatemala were discovered and reared on sugarcane (Saccharum officinarum L.). Based on these specimens, morphological and molecular characters support the status of D. postlineella as a separate species. The DNA sequence from the COI barcode region and host plant are reported for the first time. Diatraea postlineella is closely related to D. crambidoides (Grote) and D. mitteri Solis. Photographs of the adults and their genitalia, a comparison of external characters, and a table of male and female genitalia characters to identify the three species are provided. A distribution map of the three species, which includes holotype localities and specimens used for the neighbor-joining cluster analysis, is provided.