The large yellow croaker Larimichthys crocea, is a commercially important marine fish species that is susceptible to Cryptocaryon irritans in summer and mass mortality due to cold stress during overwintering. CuSO₄ is an effective and affordable treatment for C. irritans, but it causes Cu pollution in aquaculture water. This study investigated the effects of Cu acclimation on the antioxidant capacity, energy metabolism, and non-specific immunity of large yellow croaker under cold stress. Fish were pre-acclimated to 0 and 20 μg Cu/L for 7 d, and subsequently exposed to cold stress (10 ℃) for 6 and 24 h. The results showed that compared to the control group, the cold stress group showed oxidative damage via changes in the antioxidant system, energy metabolism, and immune system, as evidenced by increased reactive oxygen species (ROS), vacuolation rate of hepatocytes, chromosome coagulation, anaerobic metabolism, and reduced antioxidant capacity. Cu acclimation with low temperature stress alleviated cold stress-induced oxidative damage by improving antioxidant capacity, energy metabolism efficiency, and non-specific immunity, as evidenced by decreased vacuolation rates of hepatocytes, ROS, and lactic acid contents, and increased activities of glutathione peroxidase, catalase, ATP synthetase, succinate dehydrogenase, alkaline phosphatase, lysozyme, and contents of glutathione and ATP. Cu preacclimation can generate adaptive responses that enhance tolerance to low temperature stress, emphasizing the central role of hormesis.