Interleukin (IL)-27 has been reported to possess anti- and proinflammatory properties in several immune related-disorders, but its role in diabetic retinopathy is still elusive. Here, we aimed to (i) evaluate IL-27 concentrations in serum and aqueous humor of diabetic patients with or without retinopathy and (ii) test whether IL-27 is correlated with some risk factors of diabetic retinopathy. The study comprised 60 diabetic patients with and without retinopathy along with 20 healthy controls. Serum and aqueous humor concentrations of IL-27 were assessed by ELISA. The mean of IL-27 concentration in aqueous humor in patients with diabetic retinopathy (6.7±2.7ng/L) was significantly elevated in comparison with either diabetic patients without retinopathy (4.6±0.5ng/L) or healthy control group (4.1±0.8ng/L). Besides, IL-27 concentration in aqueous humor was positively correlated with serum glucose, lipid profile and glycated hemoglobin (HbA1c). Based on this study, IL-27 is implicated in the pathogenesis of diabetic retinopathy and positively correlates with the disorder progression.