The nucleus reuniens is the largest nucleus in the midline of the thalamus, with extensive afferent inputs and relatively limited efferent outputs. Functionally, this nucleus serves as a pivotal hub connecting the medial prefrontal cortex with the hippocampus, playing significant roles in spatial learning and memory, recognition memory, and fear memory. In addition to these basic physiological functions, recent research has demonstrated the involvement of the nucleus reuniens in various neurological disorders, such as schizophrenia, epilepsy, Alzheimer's disease, depression, and anxiety. This review summarizes the evidence on the role of the nucleus reuniens in the progression of these disorders, aiming to elucidate novel pathophysiological mechanisms underlying the onset and development of brain disorders, and to provide insights for both basic and clinical research.