A novel phylogenetic hypothesis for the subfamilies Dyopsinae and Thiacidinae is presented. For the first time, the type genus and species of Thiacidinae, Thiacidas postica Walker, is sequenced and analyzed within an expanded dataset that includes a diverse array of representative Noctuidae. Utilizing a combination of phylogenomic data and traditional phylogenetic analyses based on legacy (Sanger) sequence data, the results strongly support its placement within Dyopsinae. Thiacidas postica and other Thiacidas Walker species are placed within the Ceroctena Guenée clade (in the sense of Zahiri et al. 2013), forming a strongly supported sister relationship with the African genus Sciatta Walker. Consequently, the subfamily Thiacidinae is removed from synonymy with Pantheinae, and reinstated with tribal status as Thiacidini (stat. nov.) within Dyopsinae. This tribe includes the Old World genera Amblyprora Bethune-Baker, Sciatta, Thiacidas, and the Old World tropical Trisula Moore. Four additional tribes are recognized within Dyopsinae: Dyopsini, Desmolomini Schmidt & Zahiri, tribus nova, Momini (stat. rev.), and Litoprosopini (stat. rev.). The Neotropical genus Pachyplastis Felder is transferred from Erebidae to Dyopsinae: Desmolomini.