Fossil jacobsoniids are rarely discovered. Here the earliest representative of the enigmatic polyphagan family Jacobsoniidae is described and figured. A new species belonging to the extant genus Sarothrias Grouvelle, dagger Sarothrias cretaceus sp. nov., is preserved in the Upper Cretaceous amber from Myanmar, representing the first fossil Jacobsoniidae from the Mesozoic. Sarothrias cretaceus is most similar to the Recent species S. audax lipiski & Lobl from the Tanimbar Islands of East Indonesia, differing from it by the presence of elytral costae bearing squamiform setae, but it appears to retain several ancestral features, including the three-segmented club, non-setose and afoveate abdominal ventrite 1, and well-developed discrimen on the metaventrite. The new discovery indicates antiquity of the genus Sarothrias and the family Jacobsoniidae, suggesting that the family probably originated before the breakup of the supercontinent Gondwana, consistent with the hypothesis that the crown-group Staphylinoidea (including Jacobsoniidae) appeared about 193 million years ago. The regional distribution of the modern and fossil Sarothrias is indicative of biogeographical stasis, whereby dispersal was limited from the region of origin of the stem group.http://zoobank.org/urn:lsid:zoobank.org:pub:93C41362-D78B-4C26-9132-0D56030FB18C