A method and apparatus for filleting fishes is disclosed. The fish are cut on their underside by pairs of belly knives and pairs of rib knives, and by pairs of back knives on their dorsal sides. Between the belly knives and the rib knives are pairs of guide strips which guide the lower tail fin on the lower belly spines. Following the rib knives, a further pair of guides are provided and beneath these guides is a conveyor which acts on the underside of the backbone. Between the belly knives and the back knives, pairs of dorsal guides are provided in overlapping relationship. These individual guides are capable of adjustment to suit the shape of the fish.