Paraneoplastic disorders of the CNS result from immune responses to neuronal proteins expressed by tumors found elsewhere in the body. Limbic encephalitis, one of the most common manifestations of paraneoplastic disorders, is characterized by rapid onset of psychiatric and neurological symptoms that often culminate in severe neurological deterioration. Recent work has described paraneoplastic syndromes with prominent, and sometimes isolated, psychiatric symptoms for which patients are fi rst seen by a psychiatrist. Here the authors review the existing literature on psychiatric and behavioral manifestations of paraneoplastic disorders, the cellular mechanisms underlying these syndromes, and current treatment and outcomes. They also discuss the broad behavioral findings that highlight the need for psychiatrists to be aware of initial presentations of paraneoplastic disorders.