In the recent years a growing body of evidence links insulin resistance and insulin action to neurodegenerative diseases, especially Alzheimer’s disease (AD). The importance of insulin in ageing as well as its role in cognition and other aspects of normal brain functions are well established. The hippocampus and cerebral cortex-distributed insulin and insulin receptor (IR) have been shown to be involved in brain cognitive functions. Conversely, deterioration of IR signaling is involved in aging-related brain degeneration such as in AD and cognitive impairment in type 2 diabetes patients. Insulin administration, while maintaining euglycemia, improves memory in both healthy adults and Alzheimer’s disease patients. In the present review, some common links between AD and type 2 diabetes are presented. Furthermore, several biochemical aspects existing in both pathologies are highlighted.