Background: To reduce morbidity and mortality, awareness regarding diabetes and its complications is necessary. This study aimed to assess the level of knowledge regarding complications of diabetes mellitus among patients with type 2 diabetes in the Western Region of KSA. Methods: A cross-sectional study was conducted recruiting patients with diabetes from the Diabetes Centers at Prince Mansoor Military Hospital in Taif and Al-Noor, Hera hospital in Makkah. Overall, 571 patients with diabetes were enrolled in this study. The interviewer filled out a pretested questionnaire with face-to-face interviews. Levels of knowledge were determined by calculating the scores. Results: (n=570) agreed to be included in the study. We found that over seventy-six percent of the participants were knowledgeable about diabetes complications, as conveyed by their treating physician. Although knowledge about hyperglycemia symptoms was quite good among our participants, their knowledge about hypoglycemia symptoms was less impressive. Knowledge about diabetes complications was affected positively by a range of factors, including living in Taif, college education, and family history of diabetes. Discussion: We confirmed, in this work, that knowledge about diabetes complications is suboptimum, superficial, and lacking among Saudi patients. Recommendations: Knowledge about diabetes complications remains suboptimum among Saudi individuals. Makkah city needs to be targeted by effective educational interventions to help improve its residents’ knowledge level about diabetes complications. Educational interventions should focus on systematic complications of diabetes, particularly highlighting how diabetes causes cerebrovascular accidents and neurological problems. Future research should be longitudinal and attempt to assess the link between better knowledge of diabetes complications and their preventability. Key words: Knowledge, diabetes complications, risk factors, Saudi Arabia.