Infections of the brain in the postnatal period differ from those in older children as a result of a combination of distinct epidemiologic factors in general, and immaturity of neonatal brain and immunologic host response in particular. It has been recognized that clinical and neurologic signs are often nonspecific, sometimes scarce, and seldom correlate with the extent of neuroimaging findings, thus warranting an early MR imaging examination in the course of the disease, enabling rapid therapy institution and better clinical outcome. This article reviews most of postnatal pathogen agents involved in neonatal brain infections, related physiopathology, and neuroimaging findings.