A highly diverse fauna of dromioid brachyurans from the Serraduy Formation (lower Eocene) in the western Pyrenees (Huesca, Spain) is described and illustrated. Recorded taxa are Mclaynotopus longispinosus new genus new species, Torodromia elongata n. gen. n. sp., Basidromilites glaessneri n. gen. n. sp., ?Basidromilites sp., Sierradromia gladiator n. gen. n. sp., Kromtitis isabenensis n. sp., and ?Basinotopus sp. Other European outcrops have yielded dromioids in association with specific environments, likely coral and sponge reef and siliciclastic soft bottoms; but the present material constitutes the most diverse dromioid assemblage from the lower Eocene worldwide. These dromioids co-occurred with a rich invertebrate fauna and lived near coral–algal reef mounds. Sedimentological data suggest that most of the fauna accumulated in fore reef settings as a result of storm activity. The present material greatly increases the diversity of known dromioid crabs associated with Eocene reef environments.