Diabetic retinopathy is a major cause of blindness and one of its possible mechanisms is impairment in proteins and amino acids synthesis due to impairment in glucose synthesis. So far, different amino acids have been used to improve diabetic retinopathy. However, no research has been done till now about the effect of glycine on histological changes of diabetic rats retina. So, this is the main goal of the current study. 40 adult male Wistar rats weighing approximately 200- 250 g were prepared and divided into 4 groups of 10 each, which include: the first group (the rats were kept without receiving any material), the second group (healthy, the rats were received glycine at concentration of 130 mM, 1 %w/v), the third group (diabetic, the rats were kept without receiving any material), the fourth group (diabetic, the rats were received glycine at concentration of 130 mM, 1 %w/v). All rats were anesthetized after 16 weeks The separated retina was immersed in glutaraldehyde 4% for 3-4 h. Retina tissue was rised with buffer, post fixed in osmium tetroxide 1% and dehydrated through a graded ethanol series. The tissue was then placed in a mixture of propylene oxide and TAAB resin and transferred in pure resin. Semithin sections was prepared and viewed under light microscope (LM). Ultrathin sections were prepared, stained, and Viewed under TEM. Studies and evaluation of the thickness of IPL, INL, OPL, ONL, PSL and GCL. After preparing slides from the samples and staining with toluidine blue stain, they were examined and compared with light microscopy. The results showed that a significant decrease in the thickness of PSL and ONL and a significant increase in the thickness of IPL were observed in the group received glycine compared to the normal group (P≤0.05). There was a decrease in the thickness of all layers except PSL and IPL in the diabetic group compared to the normal group. These changes were not statistically significant. The thickness of whole retina and its layers were increased significantly in diabetic group received glycine compared to other groups (P≤0.05). Glycine increases the thickness of retinal layers in the retinopathic group through its anti-diabetic properties as well as its influence on improvement of protein synthesis in retina; so, treatment with glycine is recommended to improve different layers of retina in diabetic patients with retinopathy.