Cancer can have diverse and widespread effects on the nervous system. Knowledge of the most common characteristic mechanisms by which cancer impacts the nervous system enables prompt diagnosis and appropriate management. Here, a variety of neuro-oncologic emergencies are reviewed. Mass effect, status epilepticus, pituitary apoplexy, and metastatic epidural spinal cord compression are emergencies that arise from direct effects of central nervous system neoplasms. Limbic encephalitis may result in hospitalization and at times critical illness, and is usually caused by antibody-mediated reactions to neoplasms. Treatment-related neuro-oncologic emergencies from the effects of radiation and chemotherapy in severe cases may also result in medical emergencies.