Liver transplantation (LT) for hepatocellular carcinoma (HCC) is the treatment of choice for patients with tumor characteristics within the Milan criteria associated with Child B or C cirrhosis. LT provides the best cure for both the tumor and the cirrhosis. There have been several emerging reports that new-onset diabetes mellitus (NODM) after transplantation (NODAT) is one of the most negative predictive factors for low survival rate and related co-morbidities. Little is known about the onset of NODM in post-transplant patients and, overall, whether the pathogenesis of NODM differs from that known for the general population. Principally, it is still unknown whether NODAT is related to the primary hepatic disease, the surgical procedures, immunosuppressive treatments, or is it due to the donor liver. This review will focus on the identification of factors, in the setting of LT, which may lead to the development of NODM. Early prevention of these factors may abate the incidence of NODM and positively impact survival rate, and thus ameliorate the worsening of cardiovascular risk factors which usually occur after LT.