Jacobsoniidae, comprising a small group of small-to-minute polyphagan beetles, is a family presently placed within Derodontiformia. No fossil jacobsoniid has been described to date. Here, we describe the first fossil jacobsoniid, Derolathrus groehni n. sp., based on two well-preserved individuals in middle Eocene Baltic amber. Micro–computed tomography (micro-CT) was used to reveal many diagnostic characters of the Recent genus Derolathrus Sharp. Derolathrus groehni is compared with modern Derolathrus species and is noteworthy for the well-developed eyes and elongate prothorax.