Background: Diabetic retinopathy is the greatest and major micro-vascular diabetic complication, which can lead to preventable blindness and visual impairment among patients. Sufficient knowledge, practices and attitude for Diabetic Retinopathy can prevent serious threatening complications. Aim of the current study was to evaluate the effect of prevention instructions regarding diabetic retinopathy on patients'knowledge, practices and attitude. Study design: A Quasi-experimental research design was utilized to accomplish this study. Setting: The study was carried out at the diabetes clinic at Al-Hussein University Hospital, Cairo, Egypt. Subjects: A purposive sample of 140 patients was recruited in the current study. Tools: four tools were used for data collection, a structured interview questionnaire was the first tool. The second tool was a patients' knowledge questionnaire. The third tool waspatients' self- reported practices questionnaire. The fourth tool was the patient's attitude questionnaire. Results: This study showed a significant difference between patients' levels of knowledge, practices and attitude regarding diabetic retinopathy in the pre and post phases of preventive instructions implementation with p = (0.001) and a statistically significant correlation were found between total knowledge and practices ( p > 0.001). Moreover, a statistically significant correlation was observed between total practices and attitude post preventive instructions implementation (p > 0.05). Furthermore, there was no statistically significant correlation between total knowledge and attitude post preventive instructions implementation. Conclusion: Implementation of the diabetic retinopathy prevention instructions showed a significant improvement in patients' acquisition of knowledge and positive practice, with notable positive improvements in patient attitude. Recommendations: Ongoing patient education with the development of specific evidence-based guidelines for the prevention, detection, and management of diabetic retinopathy and endorse in the patients' prevention programs.