Atherosclerosis is a complex chronic inflammatory and metabolic disease that involves the collaboration of several cellular components of the immune system and results in thickening of the arterial wall. Atherosclerosis is also the primary cause of coronary artery and cerebrovascular diseases. A multitude of immune cell subsets, soluble molecules such as chemokines and cytokines, and circulating lipids play pivotal roles in atherosclerosis development. In this review, we highlight the role of the immune system in the course of atherosclerotic disease development and discuss the mechanisms involved.