Diabetes is a metabolic disorder due to the defect in insulin secretion or function. Many people in the world are affected by this disease. The present study investigates the preventive effect of fasting in Alloxan-Induced diabetic rats. Eighteen adult male wistar rats weighing 180 to 230 g were randomly divided into 3 equal groups including: (experimental, diabetic and non-diabetic controls) and housed in single cages. Each group consisted of 6 rats. Twenty five days before blood glucose test, the rats of the experimental group were exposed to fasting so that in 24 hours only 6 hours (6 pm to 12 pm) to chow and water were accessed and at other times they were hungry but had free access to water. This case continued for 10 days then free access to food was provided and water for all groups during second 10 days. On day 21, the non-diabetic control group was given an injection of normal saline. The experimental and diabetic control groups was given an injection of Alloxan (130 mg/kg, i.p) Data were evaluated using parametric test by one-way analysis of variance followed by Tukey post-test and non-parametric analysis Kruskal-Wallis. Results showed that fasting has a significant effect on the prevention of diabetes