Morphology and DNA sequences are used to describe a new species of New Guinea Worm-Eating Snake (Elapidae: ToxicocalamusBoulenger, 1896) from Papua New Guinea: Toxicocalamus goodenoughensis n. sp., endemic to Goodenough Island of the D'Entrecasteaux Archipelago. Toxicocalamus goodenoughensis morphologically most closely resembles T. pachysomusKraus, 2009, but it differs by having undivided nasal scales completely surrounding nares (vs. divided), pale yellow markings on supralabials (vs. purple), a yellow nape band (vs. unbanded uniform nape), a dark gray-brown dorsum (vs. medium brown), dark brown mottling on yellow ventral scales, darkening toward cloaca (vs. uniform light brown), and >175 ventral scales. Phylogenetically, T. goodenoughensis is sister to another D'Entrecasteaux endemic, T. nigrescens Kraus, 2017. Coalescent-based species delimitation found the new species to be uniquely delimited from all other taxa (n = 13) in all combinations of parameters settings. Micro-computed tomography (μCT) scanning revealed the presence of distinctive variation in postfrontal bone morphologies, with three morphotypes exhibited within the genus: directed forward, directed lateral/perpendicular to cranium, and absent. Toxicocalamus goodenoughensis was found to have a sickle-shaped and directed forward postfrontal bone. The directed forward morphotype was shared by T. loriae clade 3 (sensu Strickland et al., 2016), T. mintoni, T. nigrescens, and T. pachysomus. Our work is the most comprehensive phylogenetic analysis of the genus and the first study using μCT scanning for comparative morphology of Toxicocalamus. We also provide an updated dichotomous key for the genus.