Background: Diabetic retinopathy (DR) is the most common ocular complication of diabetes mellitus (DM) and considered one of the leading causes of blindness in developed countries. Diabetic retinopathy is predominantly a microangiopathy in which high glucose levels can make small blood vessels particularly, vulnerable to damage. Objective: The aim of this work was to assess the thickness of peripapillary retinal nerve fiber layer (RNFL) measured by Swept Source optical coherence tomography (SS-OCT) in patients with Type 2 Diabetes Mellitus (DM). Patients and Methods: The study was an observational cross-sectional study. The study was conducted on 40 eyes of diabetic patients from the outpatient clinic in ophthalmology department of Al-Azhar University Hospitals. All patients were subjected to a complete ophthalmic examination including OCT. Results: The current study showed a negative correlation between parameters related to DM (duration of DM, and state of glycemic control measured by HbA1C) and all the parameters related to RNFL, and RGCL thickness but this correlation was statistically insignificant, and there was statistically significant decrease in superior RNFL thickness in patients with mild DR than patients with no DR, however, this difference was statistically insignificant in all parameters related to RGCL thickness in the two groups. Conclusion: Optical coherence tomography (OCT) provides non-invasive, quantitative and objective measurement of RNFL thickness, optic nerve head, and RGCL thickness with high resolution and accuracy. This could be the method of choice for monitoring the neurodegenerative changes in DR.