Autism spectrum disorders (ASD) are developmental disorders characterized by behavioral deficits in verbal and nonverbal communication as well as social interactions, and are accompanied by repetitive or stereotyped behaviors and interests. Numerous studies over the last forty years have recognized altered immune responses in individuals with ASD; concurrently basic research has highlighted the myriad of neuroimmune interactions and the cross talk that occurs between nervous and immune systems. Neuroinflammation, particularly in the cerebellum, has been found in post mortem brain tissues from individuals with ASD and is characterized by the presence of profound glia activation processes. This and altered gene expression profiles indicating perturbed immune suggest a contributing role for immunological systems in the pathology of ASD. Peripheral immune abnormalities have also been found; shifts in both direction of Th1 and Th2 skewing have been reported as well as autoantibody production, increased NK cell activation, T cell responses and monocyte cell function overwhelmingly suggesting the presence of immune dysfunction in individuals with ASD. Many of these findings are associated with worsening behavioral scores, suggesting treatment of immune function could be useful in alleviating symptoms associated with ASD. Immune activation in utero is also associated with an increased risk of the child for having a diagnosis of ASD, where increased cytokine production in the offspring is directly linked to changes in offspring behavior. In addition to peripheral changes, brain and CSF immune variations in ASD are reported as well as an increase in gastrointestinal/mucosal dysfunction which has led to an increased interest in exploring the gut-brain-immune connections and its role in ASD. Further research in neuroimmune interactions may bring further insight and elicit new therapeutic tools for ASD.