We investigated the effects of the different light emitting diodes (LEDs; red, green, blue, and mixed purple) on oxidative stress by measuring the expression and activities of antioxidant enzymes, plasma $H_2O_2$, lipid peroxidation (LPO), aspartate aminotransferase (AspAT), alanine aminotransferase (AlaAT) levels, and melatonin during thermal stress (low-water temperature, $22{ ightarrow}14^{circ}C$; high-water temperature, $22{ ightarrow}30^{circ}C$) on goldfish, Carassius auratus. The expression and activity of the antioxidant enzymes and levels of $H_2O_2$, LPO, AspAT/AlaAT, and melatonin were significantly higher after the fish were exposed to low-/high-water temperature environments. Furthermore, in green and blue lights, the expression of antioxidant enzymes and mRNA of heat shock protein 70, and the activity of the antioxidant enzymes and plasma $H_2O_2$, LPO, and melatonin levels were significantly lower than those under other light spectra. The results indicated that low-/high-water temperature conditions induced oxidative stress in goldfish and green and blue LEDs inhibit oxidative stress.