Objectives This study was conducted to evaluate the effects of oral supplementation of Spirogyra algae on oxidative damages and inflammatory responses in streptozotocin (STZ)-induced diabetic rats. Methods Diabetes was induced by administration of 55 mg/kg of streptozotocin. A total of sixty-four rats were divided into eight groups of eight rats each as follows:1) non-diabetic control; 2, 3, and 4) non-diabetic rats treated with 15, 30, and 45 mg of Spirogyra algae/kg/d; 5) control diabetic; and 6, 7, and 8) diabetic rats treated with 15, 30, and 45 mg of Spirogyra algae extract. At the end of the trial, the serum concentrations of glucose, interleukin-6 (IL-6), tumor necrosis factor-a (TNF-a), malondialdehyde (MDA), glutathione (GSH), total antioxidant status (TAS), C-reactive protein (CRP), insulin, triglycerides, and cholesterol were examined by specified procedures. Results Our findings indicated that the administration of STZ significantly increased the serum concentrations of glucose, triglycerides, cholesterol, CRP, IL-6, TNF-a, and MDA and decreased the serum levels of GSH and TAS (P<0.05) in diabetic rats. Oral administration of Spirogyra alleviated adverse effects of diabetes on oxidative stress and inflammatory factors in diabetic rats (P<0.05). Conclusion It can be stated that Spirogyra algae extract can be used for treatment of diabetes likely due to prevention of oxidative stress and alleviation of inflammation in the rat model.