Type 2 diabetes mellitus is a common health problem in Saudi Arabia. Awareness of patients about the disease, its complications, preventive measures, and management modalities will play a vital role in its better control and avoidance of hazardous complications. The objective was to assess type 2 diabetic patients` awareness of DM, its complications, preventive measures, and treatment modalities. A cross-sectional study was conducted among a sample of adult type 2 diabetic patients attending the chronic diseases clinic at Alwazarat primary healthcare center in Riyadh City, Saudi Arabia. Data were collected by interviewing patients using a valid questionnaire consisting of four main sections: socio-demographic characteristics of patients, diabetes-related characteristics, awareness about diabetic complications, and knowledge about different aspects of diabetes. The study included 252 type 2 diabetic patients. The age of 29.4% of them ranged between 50 and 59 years and males represented 58.7% of the patients. The majority of patients (92.5%) were aware of the development of diabetic complications in case of uncontrolled blood sugar levels. Among those patients, the most reported source of information was diabetologists (54.1%). The overall level of diabetic patients` knowledge about diabetes mellitus, its complications, and prevention and management modalities was good among 21% of patients whereas, it was poor among 31% of them. Patients aged between 30 and 49 years, females, housewives, university graduated patients (p<0.001) and married patients (p=0.001) were more knowledgeable about diabetes compared to their peers. Additionally, patients with a longer duration of diabetes (>5 years) (p=0.001), patients who reported non-adherence to anti-diabetic medications (p<0.001), those with a family history of diabetes (p<0.001), those having their information from diabetologists (p<0.001), and reported previous clinical examination for diabetic complications (p<0.001) were more knowledgeable about diabetes than their counterparts. The majority of type 2 diabetic patients were aware of the development of diabetic complications in case of uncontrolled blood sugar levels. However, the overall level of diabetic patients` knowledge about diabetes mellitus, its complications, prevention and management modalities was good among almost fifth of patients.