Abstract Aims Although exercise is shown to improve the antioxidant defense in many organs and pathologies, little research has focused on the effect of chronic exercise training on diabetes-induced liver oxidative stress. We evaluated the effect of chronic treadmill exercise on the hepatic antioxidant enzymes and redox status in STZ-diabetic rats. Main methods Male Wistar rats were randomly assigned into control, trained, diabetic, and diabetic trained groups. Type 1 diabetes mellitus was induced via intraperitoneal injection of STZ. The animals were trained by running on a non-graded motorized treadmill 5 days weekly for a period of 9 weeks. The activity and mRNA levels of antioxidant enzymes, hydrogen peroxide generation, thiol content, and GSH/GSSG ratio were evaluated. Key findings Diabetes negatively affected the hepatic antioxidant defense as indicated by reduced SOD activity, downregulation of SOD1 and GPX1 mRNA levels, increased catalase activity, increased H2O2 production, reduced thiol content and GSH/GSSG ratio. Nine weeks of treadmill exercise training either prevented (SOD1 mRNA, GPX1 mRNA, and thiol content) or ameliorated (catalase activity, SOD activity, H2O2 generation, GSH/GSSG ratio) these diabetes hepatic effects. Significance Our data suggest that exercise training attenuates the diabetes-induced alterations on antioxidant enzymes in the liver of STZ-diabetic rats by improving the hepatic ROS scavenging and redox status. This result strongly implicates a positive effect of exercise training on diabetes-induced liver oxidative stress.