In general, cancer does not progress very rapidly, however, it sometimes causes an oncologic emergency that requires immediate treatment, depending on the location and progression of the disease. Hemorrhage, obstruction, and perforation are typical abdominal oncologic emergencies. As for gastrointestinal bleeding, endoscopic hemostasis is a common treatment of choice. Transcatheter arterial embolization is the first treatment to select in case of intra-abdominal hemorrhage caused by rupture of a hepatocellular carcinoma. Patients with upper-gastrointestinal obstruction for unresectable cancer need to be treated considering their prognoses and treatment effects. Those with colorectal obstructions with cancers first need decompression. Patients with colorectal perforation should be operated immediately to prevent septic shock. Acute obstructive suppurative cholangitis needs endoscopic retrograde cholangiography for immediate diagnosis and treatment. Abdominal oncologic emergencies have decreased due to recent diagnostic and therapeutic improvements. However, it remains a crucial disease requiring appropriate diagnoses and prompt treatment based on the conditions of the patients and disease.