Research on the declining stocks of North Atlantic cod Gadus morhua has focused on the survival of planktonic larvae as a predictor of recruitment to the fishery. Very little is known of the ecology of benthic young-of-year cod, although it has been suggested that abundance of demersal 0+ fish may be a better indicator of year-class strength than larval abundance. We studied settlement and growth of individual age 0+ Atlantic cod in situ, using visual census and visual length estimation. Newly settled cod were site-attached and defended territories around a shelter site. Territory size increased exponentially with fish length. Growth and territory size were also determined by size at settlement and by priority; fish that settled largest/earliest grew more quickly and held larger territories than smaller/later settlers. Population dynamics of Atlantic cod may therefore be regulated in the early juvenile stage by post-settlement competition. Size at settlement, in addition to the timing of settlement, may determine the competitive success of an individual.