Abstract: Background: Diabetes mellitus is one of the most common metabolic diseases. In addition to its several effects on general health, it also has a specific effect on oral health. Methods: This comparative cross-sectional study design was conducted at governmental primary health care centers in Makkah, Kingdom of Saudi Arabia. The sample size was 222 of adults living with diabetes. The data was collected by a structured survey that included close-ended questions. The data was entered and analyzed by using multiple software programs. Results: A total of 222 Diabetic patients 112 males (50.5%) of them and 110 females (49.5%), consisting of 176 (79.3%) Type 2 Diabetes and 30 (13.3%) Type 1 while there are 14(6.3%) patients did not know their diagnosis of type of diabetes. A response rate of 100% was observed, 79.7% reported that have knowledge about the effect of DM on general health while only 43.2% reported that have Knowledge about the effect of DM on oral health. 88.7% of total diabetic patients regularly Brush their teeth, on the other hand, only 33.3% reported that they do regular flossing. 84.2% of participants know the importance of routine dental visits. However, 14.9% of them go for a regular checkup while 82.2% visiting their dentist only when having dental problems. Conclusions: Diabetic patients need properly designed oral health education and screening programs to increase their knowledge and attitude toward oral health and prevent diabetic complications on oral health.