Abstract: The clinical impact of new-onset diabetes mellitus (NODM) is frequently underestimated by clinicians. NODM occurs in approximately 15–20% of renal transplant patients and 15% of liver transplant recipients. Diabetes after transplantation is a leading risk factor for cardiovascular events, with a higher prognostic value than in the non-transplant population. NODM also appears to have a negative influence on graft function, and graft survival rates after renal transplantation are significantly lower in patients who develop diabetes than in controls. Patient mortality following renal transplantation is generally found to be higher in patients with NODM, due to increased cardiovascular and peripheral vascular disease, accelerated graft deterioration and diabetes-related complications, notably infection. A renal registry analysis has reported an increase of 87% in risk of death following onset of NODM. There is also limited evidence that NODM is associated with increased risk of death in liver transplant patients. The relative incidence and severity of diabetic complications in transplant recipients have not been assessed rigorously in a clinical trial but registry data indicate that 20% of renal transplant patients with NODM experience at least one clinically significant diabetic complication within three years. Financially, the additional healthcare costs incurred over the first two years following onset of NODM amount to $21 500. Routine pre-transplant assessment of diabetic risk, with requisite modification of lifestyle, glycaemic monitoring and immunosuppressive regimens, and coupled with standardized, aggressive hypoglycaemic management as necessary, offers an important opportunity to alleviate the burden of NODM for transplant patients.