Fianoniella stenognatha sp. n. from the Columbretes Islands (Castellón, Spain) is described and illustrated. The new species is distinguished by its longer and narrower mandibles with parallel or divergent rims in the apical half, wider clypeus, hind ocelli more separated and closer to the eyes, and longer flagellar segments. Additional notes to complete the original description of the closest species, F. laeviscutum (Horstmann), are given. A key to the European species of Fianoniella is provided.