The current study aimed to investigate the therapeutic effects of 5,7-dihydroxy-6-oxoheptadecanoic acid (DHA) from Tiliacora triandra on rat models of type 2 diabetes mellitus (T2DM). T2DM was induced with a combination of high-fat diet/streptozotocin (HFD/STZ), and diabetic rats were treated with DHA (25 mg/kg) for 30 days. The body weight, fasting blood glucose (FBG), serum, and liver biochemical parameters, as well as histological evaluations of the liver and pancreas, were evaluated. Diabetic rats displayed a significant increase in FBG, serum lipid profiles (triglycerides, total cholesterol, and low-density lipoprotein cholesterol), liver function enzymes (aspartate transaminase, alkaline phosphatase, and alanine transaminase), creatinine, liver malondialdehyde (MDA), and myeloperoxidase (MPO) contents. Furthermore, insulin level and liver antioxidant enzyme activities (catalase [CAT], superoxide dismutase [SOD], and glutathione peroxidase [GSH-Px]) were significantly reduced in the diabetic rats. Whereas, treatment with DHA significantly reduced FBG, serum lipids, liver function enzymes, serum creatinine, liver MDA, and MPO contents. In addition, treatment with DHA significantly increased serum insulin level and liver SOD, CAT, and GSH-Px activities. In addition, DHA alleviated histopathological changes in the pancreas and liver caused by T2DM. These results portray the antidiabetic and antioxidative properties of DHA and can be considered as a potential treatment for T2DM.