The effects of temperature (10°C and 15°C), sexual maturity (immature and mature) and sex on instantaneous growth rates, daily feeding rates and gross growth efficiency were studied in the “Pulpito,” Octopus tehuelchus (d'Orbigny, 1834), under laboratory conditions. At 15°C, immature octopus showed higher instantaneous growth and daily feeding rates than individuals maintained at 10°C (P < 0.01). At 10°C, immature individuals showed higher daily feeding rates than mature specimens (P < 0.01). Aside from a lack of measurable growth observed in mature males, sex appears to have had no effect on either instantaneous growth or daily feeding rates in either maturity stage or temperature treatment (P > 0.05). An alternative method to compare gross growth efficiencies (GGE) among 6 treatments, based on the relationship between growth and food intake, is proposed. Immature octopuses at 10°C showed a higher GGE value than at 15°C (P < 0.05). Mature individuals at 10°C were less efficient in using food in growth than immature ones. GGE value (52%) found for immature octopus at 10°C is among the highest reported in the literature. This could have important implications for a possible rearing activity of this species. Mature males and females at 10°C showed a lower GGE (35.5%) than immature individuals held at 10°C (GGE = 52%) and 15°C (GGE = 44%). Food intake, growth and food conversion are linked processes, which in O. tehuelchus are influenced by temperature and sexual maturity. In addition, whereas classic statistical tests failed to detect any of these effects on GGE, the alternative method here proposed based on the relationship of growth versus food intake was successful.