Toxoplasmosis is a worldwide disease caused by Toxoplasma gondii which is an obligate intracellular parasite that affects warm-blooded mammals including man. T. gondii neurotropic nature made it a potential causative agent for psychiatric and behavioral disorders. T. gondii uses a complicated mechanism to gain access to the brain, where it invades different brain cells, including astrocytes and neurons forming cysts. Attention deficit hyperactivity disorder (ADHD) represents a neuropsychiatric alarm-ing concern due to its indefinite etiopathogenesis among children. Depression as major depressive disorder (MDD) is a common and serious psychiatric illness that negatively affects feeling, thinking and acting. Owing to the high prevalence of toxoplasmosis and the increased incidence of ADHD and MDD in recent years, this review studied the relationship between toxoplasmosis and each of ADHD and MDD.