Mitochondrial dysfunction plays a role in the pathogenesis of a wide range of diseases that involve disordered cellular fuel metabolism and survival/death pathways, including neurodegenerative diseases, cancer and diabetes. Cytokine, virus recognition and cellular stress pathways converging on mitochondria cause apoptotic and/or necrotic cell death of β-cells in type-1 diabetes. Moreover, since mitochondria generate crucial metabolic signals for glucose stimulated insulin secretion (GSIS), mitochondrial dysfunction underlies both the functional derangement of GSIS and (over-nutrition) stress-induced apoptotic/necrotic β-cell death, hallmarks of type-2 diabetes. The apparently distinct mechanisms governing β-cell life/death decisions during the development of diabetes provide a remarkable example where remote metabolic, immune and stress signalling meet with mitochondria mediated apoptotic/necrotic death pathways to determine the fate of the β-cell. We summarize the main findings supporting such a pivotal role of mitochondria in β-cell death in the context of current trends in diabetes research.