Lipoic acid (LA) has been reported as a potential therapeutic agent due its antioxidants proprieties. It was considered its effect in different organs (gills, brain, muscle and liver) of the fish Corydoras paleatus (Callychthyidae). LA (70 mg/kg of body mass) was added to a commercial fish diet, organisms being fed daily (1% body weight). Sixty animals (mean mass: 2.37+/-0.09 g) were placed randomly in aquariums and received (+LA) or not (-LA) lipoic acid enriched diet during four weeks. After, fish were killed and the brain, muscle, gills and liver were dissected. LA treatment reduced significantly (p<0.05) reactive oxygen species concentration in brain and increased (p<0.05) glutamate-cysteine ligase activity in brain and liver of the same experimental group. LA fed organisms showed higher (p<0.05) brain glutathione-S-transferase activity, indicating that LA improves the detoxification and antioxidant capacity face components that waste glutathione in phase II reactions. A conspicuous reduction of protein oxidation was observed in muscle and liver of +LA organisms, indicating that the treatment was also effective in reducing oxidative stress parameters.