Diabetes mellitus (DM) is characterized by hyperglycemia and alterations in the metabolism of lipids, carbohydrates, and proteins. Due to its hypoglycemic effect Vochysia rufa is frequently used in Uberlandia, Brazil, to treat DM. Despite its popularity, there is little information about its effect on hepatic tissue. Therefore, we evaluated the histoarchitecture, oxidative stress parameters, and polyploidy of liver tissue from streptozotocin- (STZ-) induced diabetic rats treated with aqueous extract of Vochysia rufa (AEV). Histology was determined by fixing the livers, processing, and staining with HE. Oxidative stress was determined by evaluating CAT, GPx, and SOD activity in liver homogenates and hepatic mitochondria fraction and by measuring GST, GSH levels and lipid peroxidation (MDA). Polyploidy was determined by subjecting isolated hepatocyte nuclei to flow cytometry. In the diabetic group, GST activity and GSH rates decreased whereas liver homogenate analysis showed that GPx, SOD activity and MDA increased. AEV treatment restored all parameters to normal levels. The oxidative stress analysis of hepatic mitochondria fraction showed similar results. Lower polyploid cell populations were found in the diabetic rat livers, even after glibenclamide treatment. Thus, AEV treatment efficiently reduced hepatic oxidative stress caused by STZ-induced diabetes and produced no morphological changes in the histological analysis.