The Norwegian population of the nominate subspecies of Lesser Black-backed Gull, Larus fuscus fuscus, has declined strongly but the causes are unknown. The diet of these gulls breeding in two regions on coast of northern Norway was assessed over five years (2005–2009). In the southern region, chicks (n = 58) were fed predominantly gadoids (∼75% ABP [aggregated percentage of prey biomass] and ∼80% frequency; 70–130 mm length), probably saithe, Pollachius virens, whereas 0-group herring, Clupea harengus (40–50 mm length) accounted for ∼20% ABP and were fed to ∼20% of the chicks. In the northern region (n = 23), slightly larger 0-group herring comprised ∼60% of the prey mass and were fed to 65% of the chicks. In this area, gadoids and sandeel, Ammodytes spp., each accounted for ∼17% ABP of prey, and were fed to 20% and 30% of the chicks, respectively. Other species made up smaller proportions of chick diets. For adults, only regurgitated pellets (28 in the southern region) were available. Of 23 pellets from 2006 and 2007, 17 (74%) contained pipefish (probably Snake Pipefish, Entelurus aequoreus), whereas three contained herring, two gadoids, and one sandeel. In the poor breeding season of 2009, adult gulls also fed on blue mussels, Mytilus edulis, crabs (Brachyura), sea urchins (Echinoidea) and seabird eggs. Thus, Northern Lesser Black-backed Gulls are probably mainly piscivorous during breeding, and other prey are probably exploited only when fish are not readily available. Further, herring seems to be less important for L. f. fuscus than previously thought.