This study elucidated the impacts of coenzyme Q10 (COQ10) supplementation in a high-fat diet on growth, lipid metabolism, and mitochondrial function in spotted seabass (Lateolabrax maculatus). Totally five diets were formulated: a diet with normal fat content (11% lipid, NFD), a high-fat diet (17% lipid, HFD), and three additional diets by supplementing 5, 20 or 80 mg/kg of COQ10 to the HFD. After an 8-week culture period, samples were collected and analyzed. The results demonstrated that COQ10 inclusion prevented the HFD-induced deterioration of growth performance and feed utilization. COQ10 alleviated the deposition of saturated fatty acids following HFD intake and promoted the assimilation of n-3 and n-6 polyunsaturated fatty acids. Moreover, COQ10 administration inhibited the surge in serum transaminase activity and reduced hepatic lipid content following HFD ingestion, which was consistent with the results of oil red O staining. In addition, HFD feeding led to reduced hepatic citrate synthase and succinate dehydrogenase activities, and decreased ATP content. Notably, COQ10 administration improved these indices, and up-regulated the expression of mitochondrial biogenesis-related genes (pgc-1α, pgc-1β, nrf-1, tfam) and autophagy-related genes (pink1, mul1, atg5). In summary, supplementing 20-80 mg/kg of COQ10 in the HFD promoted growth performance, alleviated hepatic fat accumulation, and enhanced liver mitochondrial function in spotted seabass.