The aim of this study was to test the effect of copper supplementation in a formulated feed on the growth, feed efficiency, and nutritional composition of subadults Octopus vulgaris, with particular reference to the differences in the content of copper in the tissues (muscle, digestive gland, and hemolymph). Two formulated feeds were supplied to subadults octopuses kept individually for 56 days: Basal diet [11.6 mgCu/kg dry weight (dw)], and another feed with a similar composition but including a copper supplementation (copper diet: 115.2 mgCu/kg dw). No significant differences (P > 0.05) were detected in the respective growth rates (0.88% body weight/day), FE (79.5%–82.1%), proximate composition, hemolymph hemocyanin (1.6–1.8 mmol/L), hemolymph copper (0.19–0.20 mgCu/mL), or muscle copper levels (22.7–23.2 mgCu/kg dw). No significant changes were detected on proximate composition, hemocyanin and hemolymph, and muscle copper levels between animals fed formulated feeds and an initial group fed natural diet based on crab and fish (P > 0.05). The only parameter which showed a significant difference (P < 0.05) was the copper level in the digestive gland: 1,797, 390, and 1,148 mgCu/kg dw for initial (natural diet), basal and copper diet, respectively (P < 0.05). Considering the experimental conditions of this study, copper supplementation is not effective in improving the performance of a formulated feed for octopus.