Post-transplantation diabetes mellitus (PTDM) is a serious complication after organ transplantation, which could lead to cardiovascular morbidity and mortality. The rate of PTDM increased in recent years, probably due to new immunosuppressive drugs such as Tacrolimus. In this study, we retrospectively evaluated the frequency of PTDM and related risk factors in 644 non diabetic patients who underwent renal transplantation. Data was analyzed by chi-square and Fisher's exact test in SPSS software ver11.5. Among 644 patients PTDM developed in 10.2% similar to literature. PTDM was significantly correlated to age (P value = 0.000), positive familial history (P= 0.003) and HBV infection (P= 0.046). In conclusion, PTDM is not uncommon in Iranian patients and a positive family history of diabetes, HBV infection and older age increases the likelihood to develop PTDM.