From the Oligocene (Chattian) marls of the Trbovlje Formation, exposed at the Neža locality, Slovenia, a brachyuran crab (Malacostraca: Brachyura) association consisting of three taxa is described. The material presented here includes as many as 15 near-complete crab specimens from the Upper Oligocene of Slovenia does not only allow direct comparison with extant hymenosomatids, but the identification of important diagnostic characters permit classification of the fossils in question within extant genera, i.e., Halicarcinus White, 1846, and Lucascinus Poore, Guinot, Komai, and Naruse, 2016. The newly erected species, Halicarcinus popeius sp. nov. and Lucascinus trifailensis sp. nov., are considered herein the first reliable occurrences of the family Hymenosomatidae MacLeay, 1838, in the fossil record. Previously reported occurrence of hymenosomatid crabs from the Cretaceous of Brazil is disputed herein. The hymenosomatid association from the Neža locality is accompanied with the portunid crab, Necronectes cf. michelini A. Milne-Edwards, 1860, documented by an incomplete claw.