The aim of this work was to study the histological, and immunohistochemical effects of alloxan-induced diabetes and insulin treatment on the tight junctions in rats' submandibular salivary gland. Fifty adult male albino rats were used in this study. The animals were divided into two groups: Group A (control group): 5 rats, Group B (Diabetic group): 45 rats received a single intraperitoneal injection of Alloxan Monohydrate with a dose of 140 mg/kg. This group was subdivided into three sub-groups: Sub Group B1: Uncontrolled diabetic composed of 15 rats. They received no insulin treatment, scarification was done after 4 weeks (28 days),Sub Group B2: Controlled diabetic composed of 15 rats. They treated with insulin (8-15 U daily subcutaneous injection) for 3 days, scarification was done after 31 days, Sub Group B3: Controlled diabetic composed of 15 rats. They treated with insulin for 7 days, scarification was done after 35 days. The submandibular glands were stained by H&E and Claudin-4 immunostaining. We found that diabetes mellitus is accompanied by histological and immunohistochemical changes in the salivary glands, Alterations in the secretory function of the salivary glands of diabetic patients and xerostomia may be attributed to the structural loss the tight junctions in diabetic salivary glands. Insulin treatment can reverse histopathological changes and restore the tight junctions.Such knowledge is useful for knowing that The maintenance of normal structure of the tight junctions and function of salivary glands may in part be insulin dependent.