Background: successful treatment of patients with type 2 diabetes mellitus (DM) is achieved by having a HbA1C of<7%. Objectives: to determine the factors that affect successful control of diabetes mellitus type 2 at Diabetic centre, King Khalid hospital, Ministry of Health, Tabuk, KSA. Subjects and Methods: a cross-sectional study was carried out at Diabetic centre, King Khalid hospital, Ministry of Health, Tabuk, KSA. A representative sample of adult diabetes mellitus type 2 patients (18-60 years) both sexes, who attend diabetic center clinics during month of November 2016 were included. Self-administer questionnaire was used for data collection. Last HBA1c level was addressed. Results: almost one-third of the participants (n=342), aged between 41 and 50 years (35.1%) whereas 11.4% aged over 50 years. Male patients represent 65.8% of them. The duration of diabetes was more than 10 years in 45.6%. Diabetic complications were reported by 26% of diabetic patients. Regarding diabetes therapy, a combination of oral hypoglycemic and insulin was reported by 21.1% of them while insulin alone and oral hypoglycemic alone were reported by 42.1% and 36.8% of the participants, respectively. It is evident that DM was controlled among only 32.5% of the diabetic patients (HBA1C was less than 7%) while it was uncontrolled among almost two-thirds of them (67.5%). Logistic regression analysis revealed that patients aged between 41 and 50 years were at lower risk compared to those aged 20-30 years (OR=0.13, p=0.008). Females were less likely compared to males to have uncontrolled diabetes (OR=0.25, p=0.007). Patients having more than three children were at higher risk for uncontrolled diabetes opposed to those without children (OR=11.19, p=0.003). Patients having income ranged between 10001 and 15000 were more protective than whose income was ≤5000 SR/month to develop uncontrolled diabetes (OR=0.22, p=0.007). Patients without diabetic complications were less likely to have uncontrolled diabetes compared to those with complications (OR=0.24, p=0.004). Patients treated with either insulin alone or a combination of insulin and oral hypoglycemic (OHGs) were at higher risk for uncontrolled diabetes compared to those treated with OHGs alone (OR=3.51 and 3.07, p=0.007 and 0.027. respectively). Patient who never compliant with diabetic diet were more prone to uncontrolled diabetes (OR=15.09, p<0.001). Conclusion: the study revealed relatively high prevalence of poor glycemic control as expressed by HbA1c≥7%. There is a strong need for public education programs and for promoting public awareness about control of blood glucose level in Saudi Arabia.