Carotid-esophageal fistula (CEF) could be a serious complication of esophageal cancer in a patient receiving radiotherapy. We reported a 47-year-old male patient with advanced cervical esophageal cancer under radiotherapy who developed CEF with the presentations of unstable vital signs and disturbances of consciousness. Carotid-esophageal fistula-associated life-threatening conditions of carotid blowout syndrome and cerebral gas embolism were diagnosed after presentation. Subsequently, intramural dissection of esophageal and gastric walls, profound hemoperitoneum, and hypovolemic shock occurred. When a patient who had an underlying cervical esophageal cancer treated by radiotherapy develops unstable vital signs and neurological symptoms, CEF should be kept in mind in the differential diagnoses. Physicians must be alert of the associated complications of carotid blowout syndrome and cerebral gas embolism and perform timely management including decompression, fluid resuscitation, and aggressive endovascular procedure when indicated.