Background Although post transplantation diabetes mellitus (PTDM) was recognized as important complication after heart transplantation (HT), data are limited about clinical course and outcomes of PTDM. Method Between 1997 and 2010, a total of 54 patients developed PTDM after heart transplantation. The charicteristics and clinical outcomes of patients with PTDM were compared with 140 patients without diabetes mellitus. PTDM was diagnosed as fasting blood glucose levels of 126mg/dl or greater which was confirmed by repeated tests during the outpatient follow up after HT. Result The mean age of PTDM patients were significantly higher than controls (48.4짹9.9 vs. 38.7짹13.3 years, p=0.001) and the ischemic heart disease was more common indication of HT in PTDM group (20.4% [11/54] vs. 7.1% [10/140], p=0.008). After HT, there was a trend of more tacrolimus based immunosuppresion in PTDM group (38.9% [21/54] vs. 25.7% [36/140], p=0.08), although statistical significance was not reached. In multivariate logistic regression analysis, age (per 10 years) was only associated with PTDM development (Odds ratio 1.91; 95% confidence interval 1.43~2.54, P=0.001). In 18 patients (33%), PTDM was reversed during follow-up period and the reversal of PTDM was critically depends on the time taken to develop PTDM (1.1짹1.5 vs. 13.7짹25.8 months, p = 0.006). Although, the 5-year infection-free survival (after 6 months) was lower in PTDM patients (69.6짹7.1 vs. 84.7짹3.3%, p=0.031), the overall survival rate was not different (92.9짹4.1 vs. 85.8짹3.2%, p=0.220). Also, the 5-year coronary vasculopathy-free survival (81.0짹4.8 vs. 78.1짹8.7%, p=0.420) and rejection- free survival (80.4짹3.4 vs. 87.6짹4.6%, p=0.302) were not different between two groups. Conclusion The PTDM is reversible disease in some patient and not a critical factor of patient survival after HT.