Paraneoplastic neurologic syndromes (PNS) are a group of neurological disorders that are possibly caused by immunological mechanisms triggered by an underlying tumor that involves every part of the nervous system. Autoantibodies were categorized according to the risk of cancer association. Antibodies against intracellular proteins are excellent markers for tumor detection, however, without functional roles in neuronal loss, the direct effector of neuronal damage is thought to be cytotoxic T cells. The frequently associated symptoms include limbic encephalitis, cerebellar ataxia and sensory neuronopathy. The associated tumors are mainly small-cell lung cancer, breast/ovarian/uterine cancers, and thymoma. Timely diagnosis, prompt immunotherapy, and treatment of the underlying tumor are essential for managing PNS. However, we need to be cautious about the high frequency of false-positive/negative results of antibodies using commercial antibody tests. This highlight the importance of the careful evaluation of clinical features. Recently, PNS emerged after immune check point inhibitor administration, and this became a subject of attention exploring its pathogenesis. Other basic studies to understand the immunological background of PNS have been progressing.