Type 2 diabetes mellitus and metabolic syndrome are two highly prevalent clinical entities in our population and threaten to become a true pandemic. While there are still gaps in medical knowledge about the pathophysiological mechanisms leading to the development of both conditions, a significant effort has been made to study them in detail. Inflammation has been recognized as a major player in all this, and the advancement of knowledge in this area has been fruitful. This chapter will address the inflammatory mechanisms underlying these entities, starting with a more mechanistic and molecular perspective and ending in a more clinical setting.