Pericytes build together with endothelial cells the microvascular vessel wall. They have been mainly implicated in angiogenesis and maintenance of the blood brain barrier, but there is accumulating evidence for an immunological function of pericytes. Occupying a strategic position between the blood stream and the interstitial space, pericytes are able to sense environmental cues from both sides in an organ-specific manner and serve as gatekeepers for innate immune cells. In addition, pericytes are able to interact with leukocytes mediated by adhesion molecules as well as chemokines and are involved from the development of leukocytes in the bone marrow to their migration to injured or infected areas in target tissues. During disease processes pericytes regulate blood flow, vascular permeability, and leukocyte recruitment, but also contribute to maladaptive tissue responses, such as fibrosis making pericytes an attractive therapeutic target.