Toxoplasma gondii (Toxoplasma) is an intracellular parasite that infects warm-blooded animals, including humans, and has a high affinity for the central nervous system (CNS). Toxoplasma infection poses a risk in several medical fields, including obstetrics (congenital toxoplasmosis), ophthalmology (ocular toxoplasmosis), transplantation, oncology, and the AIDS epidemic (toxoplasmosis in immunocompromised patients). These diseases often cause severe neurological and ocular consequences due to inflammation and widespread necrosis in the brain and eyes. Latent toxoplasmosis was previously considered harmless for immunocompetent individuals, but epidemiology studies have linked it to multiple neuropsychiatric disorders. For example, exposure to Toxoplasma during pregnancy, early life, or in the elderly has been linked to mental retardation, schizophrenia, autism, cognitive deficits, and Alzheimer’s disease. The incidence of toxoplasmosis is determined by both parasite and host factors. As Toxoplasma is located mainly in the brain during chronic infections, the parasite is well placed anatomically to mediate brain function and affect host behaviors. However, the mechanisms by which latent toxoplasmosis may affect human behavior remain unclear due to the difficulty of accessing post-mortem material. Studies on animals have found pathological connections between latent toxoplasmosis and neuropsychiatric diseases. This connection is characterized by widespread neuroinflammation and various neuropathologies in brain connectivity, synaptic integrity and plasticity, and neural morphology and function. This chapter reviews the clinical manifestations and behavioral abnormalities in clinical and latent toxoplasmosis and the neurological background and neuropathogenesis discovered in animal studies.