Post-transplant diabetes mellitus (PTDM) is a frequent and serious complication in renal transplantation. Estimates of the incidence of PTDM after renal transplantation vary between 2% and 54%. The aim of the present study was to evaluate the incidence and risk factors of PTDM in our renal transplant patients. In this study, 102 consecutive non-diabetic patients (male/female = 62/40; age, 38.6 ± 14.5 years) with end stage renal disease (ESRD) who received kidney transplantation for the first time at our centers since 2005 were evaluated. Follow up was 12 months and two patients passed away during this time. All patients received the same protocol of immunosuppressive therapy. PTDM was defined according to the 2003 American Diabetes Association and World Health organization experts committee definition. In total, 10/100 patients (10%) developed PTDM at 12 months following renal transplantation. Patients with post-transplant diabetes mellitus were significantly older (P = 0.013) and had higher body mass index (P = 0.001). There were significant differences (P < 0.05) between PTDM and non-PTDM patients in respect of systolic blood pressure, serum triglyceride, duration of renal replacement therapy before transplantation and peritoneal dialysis as previous renal replacement therap. There were no differences between two groups with regard to positive family history of diabetes mellitus, gender, and positive history of acute rejection, positive history of steroid pulse therapy and etiology of ESRD. On performing multivariate analysis, the only parameter found to be associated with PTDM was the body mass index (P = 0.04). The incidence of post-transplant diabetes mellitus in our renal transplant patients was 10% at 12 months following transplantation and the most important factor associated with PTDM was a higher body mass index (P = 0.04).