Most data of fish feeding on cnidarians were obtained from the studies on gut contents of the predators rather than in situ observations. The feeding observation of Boops boops on Geryonia proboscidalis was observed in September 2013, in Sığacık Bay, the Aegean Sea, Turkey. The four bogue specimen was approximately 10-12 cm in total length (TL), and two out of six tentacles and tip of oral arm of G. proboscidalis was extirpated before the incidence. B. boops individuals directly attacked the intact tentacles of the hydrozoan, and extirpated rest of them in a minute. The present observation is also the northernmost record of G. proboscidalis from the Turkish coasts.