Four new species of the braconid wasp genus Hecabolus Curtis, 1834 (Doryctinae Foerster, 1863) are described for the Neotropical region in south and southwestern Brazil: H. acutus sp. nov., H. chrisaxeli sp. nov., H. gavinbroadi sp. nov., and H. transversalis sp. nov. We also report the morphological variation of females and males of H. mexicanus Zaldívar-Riverón & Belokobylskij, 2009, originally described based on a single female, and provide its first precise geographical distribution records. An updated key to the 13 described species of Hecabolus is provided.