The growing global incidence of diabetes mellitus is a major problem in both developed and developing countries and the limitations associated with currently available treatments have shifted researchers' focus to naturopathy. Herbal plants have been utilised for the treatment of diabetes since ancient times as they are less poisonous and have fewer adverse effects than synthetic ones. We isolated and purified two novel chemicals (Phytol and 2- Methyl hexadecan-1-ol) from Waltherica indica hydroalcoholic extract in prior investigations. The goal of this work was to assess the in vivo antidiabetic activity of W. indica hydroalcoholic extract in streptozotocin-induced experimental diabetes, as well as to determine their likely mechanism of action. For 45 days, STZ (55 mg/kg b.wt) induced diabetic rats were given the extract orally at doses of 50 and 100 mg/kg b.wt. In diabetic rats, treatment with hydroalcoholic extract significantly (P < 0.05) reduced blood glucose and glycosylated haemoglobin levels while also restoring body weight, liver glycogen content and serum insulin levels in a dose-dependent manner. For the in vivo investigation, six animals were divided into five groups: control, diabetic control, standard control, low dosage and high dosage. The body weight, body temperature and blood glucose levels of all the animals were measured. Following the treatment, biochemical parameters: triglycerides, cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), alkaline phosphatase level (ALP), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), total protein and alkaline phosphatase level (ALP), serum glut (ANOVA) were calculated. On the 45th day, all of the animals were slaughtered and the pancreas tissue was histopathologically examined. Group V administered with 80 mg/kg body weight had a substantial effect after comparing different biochemical parameters and histoarchitecture of the different test groups of animals.