In this study, we investigated the inhibitory effects of m-coumaric acid on the glycosylation of proteins in the retinas of diabetic rats. Male rats were divided into two main groups, Group I (normal control) and Group II (diabetic); Group II was further divided into four subgroups: Group IIa (diabetic control), Group IIb (diabetic rats were given m-coumaric acid orally [150 mg/kg, body weight (bw)/day]), Group IIc (diabetic rats were given HCA m-coumaric acid orally [300 mg/kg bw/day]), and Group IId (diabetic rats were given insulin [10 units/kg bw/day]) as a positive control). The treatment lasted for six weeks, and the data obtained suggested that m-coumaric acid reduced glucose and glycated hemoglobin levels, which further decreased the formation of glucose-derived advanced glycation end products. Hence, it protected the tissues from the detrimental effects of hyperglycemia and enhanced antioxidant activity. In conclusion, m-coumaric acid could be a potential candidate to prevent the onset and progression of retinopathy in diabetic patients.