Background: Diabetic retinopathy (DR) is a highly prevalent complication for DM patients. It may be a leading cause of visual impairment among vital groups of population. This study aimed to assess the retinal structure and function using Optical coherence tomography angiography (OCTA) and multifocal electroretinogram (mfERG), respectively, in eyes with and without DR and interrelationship between retinal structure and function. Methods: This prospective study included 60 eyes of 60 patients who undergone assessment of OCTA and mfERG. Patients were divided into 3 equal groups: Group 1: included normal individuals without diabetes mellitus, group 2: diabetic patients without DR Group 3: diabetic patients with DR. Results: In Diabetic patients without retinopathy, we found a good positive correlation between Cub Avg. thickness and mfERG in Ring 2 Resp den. FAZ area and Ring 5 Resp den. FAZ perimeter and Ring 4 Resp den, and Ring 5 Resp den. And A good negative correlation between Cub Avg. thickness and Ring 5 p1. Implicit time, while in patients with retinopathy we found a good positive correlation with Ring 1 Resp den, Ring 5 p1. implicit time and FAZ area. Conclusion: Both OCTA and mfERG are beneficial to early detect diabetic macular changes and can detect morphological and functional retinal changes related to diabetes. Both vascular and functional impairment assessed by OCTA and mfERG respectively and their parameters become more severe by increasing the severity and progression of DR.