Post-transplant diabetes mellitus (PTDM) is a frequent and relevant complication after renal transplantation: it affects 20-30% of renal transplant recipients and increases the risk for cardiovascular and infectious events. Thus, understanding pathogenesis of PTDM would help limiting its consequences. In this review, we analyse novel aspects of PTDM, based on studies of the last decade, such as the clinical evolution of PTDM, early and late, the reversibility rate, diagnostic criteria, risk factors, including pre-transplant metabolic syndrome and insulin resistance (IR) and the interaction between these factors and immunosuppressive medications. Also, we discuss novel pathogenic factors, in particular the role of β-cell function in an environment of IR and common pathways between pre-existing cell damage and tacrolimus-induced toxicity. The relevant role of prediabetes in the pathogenesis of PTDM and cardiovascular disease is also addressed. Finally, current evidence on PTDM treatment is discussed.