Primary diabetes mellitus and post–transplant diabetes mellitus has been linked to graft and patient–related complications, including graft loss, cardiovascular disease and infection. It is a major cause of these complications and mortality. The aim of this study was to evaluate the complications. In this historical cohort research, 111 patients were studied from 1996 to 2004.Patients were studied in 3 group, A: non-diabetic patients pre- and post transplant (controlled group), B: primary diabetic patients, C: post-transplant diabetes mellitus. 72.9 percent of the subjects were male and others were females. Delayed graft function was occurred in 2.7, 8.9 and 10.9 percent, rejection in 7.2, 14.2 and 16.3 percent and mortality in 2.7%, 12.5 and 5.4 percent of group A, B and C respectively. There is no significant difference between incidence of complications in group B and C. Chi square showed incidence of delayed graft function, rejection and mortality between group A and each of B and C were significant, p=0.027, R=3.67 and CI 0.95, p=0.004, RR=2.45 and CI 0.95, p=0.045 RR=3.33 CI 0.95, respectively. According to the results obtained, it seems that post-transplant diabetes mellitus and primary diabetes mellitus are major risk factors and must be exactly followed up prior to and post kidney transplantation. It is recommended more study to modify proper and better treatment is recommended.