Marine gastropods are consumed worldwide due to their nutritional quality, having important economic value in international markets. In the gulfs of Northern Patagonia (Argentina), marine gastropods are captured as complementary resources during bivalve artisanal fisheries. In this study, we determined the biochemical composition during the reproductive cycle of four edible marine gastropods abundant along the South-western Atlantic coast: Odontocymbiola magellanica, Buccinanops deformis, Buccinanops cochlidium and Trophon geversianus. All the studied species presented high protein (36–70.8%), low lipids (0.02–1.50%) and intermediate glycogen content (3.22–14.08%). The main oviposition season was during spring and summer. The mean nutritional values indicate that the species studied provide a good source of nutrients appropriate to the human diet, reaffirming their value as a commercial resource. Taking into account the nutritional contribution and the reproductive season, the best period for the capture of these resources is during summer for O. magellanica and T. geversianus, and during autumn for B. deformis and B. cochlidium. This work will help promote the consumption of Patagonian gastropods while ensuring their responsible capture, contributing to the sustainability of these valuable resources.