We aimed to investigate the relationship between serum osteoprotegerin (OPG) level and glycemic control, lipids, renal function, microalbuminuria, insulin resistance and markers of atherosclerosis including C-reactive protein (CRP), fibrinogen and erythrocyte sedimentation rate (ESR) in patients with type 2 diabetes mellitus (DM). A total of 166 patients (99 women and 67 men) with type 2 DM were recruited in the study. Serum OPG level was higher in poorly controlled diabetic patients (HbA(1c) ≥ 7%) than in well-controlled diabetic patients (HbA(1c) < 7%) [4.0 (3.6-5.0) and 3.5 (2.9-4.4) pmol/L, p = 0.02]. There was no difference between the patients with and without microalbuminuria with respect to OPG levels (p > 0.05). LogOPG was correlated with age (r = 0.47, p = 0.0001). After adjustment for age, sex and BMI, logOPG correlated positively with fasting blood glucose (FBG) (r = 0.28, p = 0.001), prandial blood glucose (PBG) (r = 0.22, p = 0.009), glycated hemoglobin (HbA(1c)) (r = 0.26, p = 0.002), logHOMA-IR (r = 0.30, p = 0.006), fibrinogen (r = 0.17, p = 0.04), mean albumin excretion rate (MAER) (r = 0.20, p = 0.01) and negatively with creatinine clearance (r = - 0.20, p = 0.01). Regression analysis revealed that logOPG was independently associated with age (p = 0.0001), HbA(1c) (p = 0.01) and MAER (p = 0.02) (r(2) = 0.25). In conclusion; we found that serum OPG levels are increased in poorly controlled type 2 DM and associated with age, glycemic control and microalbuminuria.