ABSTRACT There is evidence that indicates that temperature modulates the reproduction of the tropical species Octopus maya, through the over- or under-expression of many genes in the brain. If the oxygen supply to the brain depends on the circulatory system, how temperature affects different tissues will begin in the heart, responsible for pumping the oxygen to tissues. The present study examines the impact of heat stress on the mitochondrial function of the systemic heart of adult O. maya. The mitochondrial metabolism and antioxidant defense system were measured in the systemic heart tissue of female organisms acclimated to different temperatures (24, 26, and 30°C). The results show that acclimation temperature affects respiratory State 3 and State 4o (oligomycin-induced) with higher values observed in females acclimated at 26°C. The antioxidant defense system is also affected by acclimation temperature with significant differences observed in superoxide dismutase, glutathione S-transferase activities, and glutathione levels. The results suggest that high temperatures (30°C) could exert physical limitations on the circulatory system through the heart pumping, affecting nutrient and oxygen transport to other tissues, including the brain, which exerts control over the reproductive system. The role of the cardiovascular system in supporting aerobic metabolism in octopus females is discussed.