Abstract: Iodine is an essential micronutrient for humans, and inadequate iodine status can negatively impact neurological development and function. Currently, iodine nutritional issues in the population remain a concern. Numerous epidemiological studies have confirmed that severe iodine deficiency causes a series of neurological dysfunctions, while the adverse consequences and related mechanisms of mild/moderate iodine deficiency or excess on the nervous system have not been fully elucidated. This article reviews epidemiological studies related to mild/moderate iodine deficiency, iodine excess, and neurological function, as well as their possible mechanisms of action. This review aims to provide a theoretical basis for the prevention and treatment of the neurological effects of inadequate iodine nutrition.