A new cancer diagnosis is expected to affect approximately 1.9 million people in the United States in 2021. A small percentage of these patients will experience an emergent cancer-related complication. Oncologic emergencies may be encountered in emergency departments or require intensive care management. Patients newly diagnosed with cancer are more likely to present with emergencies related to the underlying malignancies. Oncologic emergencies can have various manifestations, ranging from mechanical obstruction due to tumor growth to metabolic derangements due to abnormal secretions from the tumor. Therefore, early identification and treatment of life-threatening oncologic events is critical. Although there are several different types of oncologic emergencies, this article focuses on metabolic emergencies (tumor lysis syndrome and cytoreductive hyperthermic intraperitoneal chemotherapy) and structural emergencies (increased intracranial pressure and vena cava thrombus). The purpose of this article is to provide acute care clinicians with an overview of selected oncologic emergencies and their evidence-based management.