The invention relates to a device (10) which is designed and configured for processing headed fish (11), namely for cutting the fish fillets off the side bones, said fish fillets preferably already having been processed with an abdominal blade assembly and a back blade assembly, comprising a transport device (12) which is designed and configured for transporting the fish (11) in the transport direction (T), tail first, wherein the transport device (12) has a continuously circulating transport conveyor (13) with at least one transport saddle (14) for receiving and securing a fish (11), a side blade assembly (15), wherein the side blade assembly (15) has two side blade units (16, 17) which are opposite one another on both sides of the transport conveyor (13) in the region of a transport saddle guide (18), and each side blade unit (16, 17) has a rotationally drivable circular blade (19, 20) and a counter-surface assembly (21, 22) for the circular blade (19, 20), wherein the circular blade (19, 20) is arranged at
