: Diabetes mellitus and Alzheimer’s disease are considered the most prevalent diseases in older ages worldwide. The main pathology of Alzheimer’s disease is highly related with accumulation of misfolded proteins that lead to neuronal dysfunction in the brain. On the other hand, diabetes mellitus is associated with alteration of insulin signaling, which could cause the reduction of glu-cose uptake, metabolic prohibition of energy consuming cells, as well as suppression of glucose to fat conversion in the liver. In spite of having seemingly different pathological features, both dis-eases share common underlying biological mechanisms. Besides, the epidemiological and envi-ronmental links between these two diseases should not be overlooked. In this study, we aim to review shared pathological mechanisms of Alzheimer’s disease and diabetes mellitus, including impaired glucose metabolism, increased Amyloid-Beta (Aβ) production, impaired lipid metabo-lism, mitochondrial dysfunction, increased inflammation and elevated oxidative stress. Further-more, we discuss epidemiological/environmental association between these two diseases and also review animal investigations, which have evaluated the potential links between the two diseases.