Prey size selectivity in piscivorous fish larvae is important to both aquaculture and fisheries science, but laboratory experiments are few. We analyzed selective foraging in Atlantic bluefin tuna larvae (Thunnus thynnus) using two larval fish prey species. The experiments revealed that selective foraging of prey sizes differed among bluefin tuna predator sizes (15–25 mm SL) and prey species, bonito (Sarda sarda) and seabream (Sparus aurata). The observed pattern suggest a general preference for small bonito prey larvae but large seabream prey. Thus, prey size alone is not the only trait responsible for size selectivity in piscivorous fish larvae.