Pneumopericardium is defined as the collection of air inside the pericardium. Gastro-pericardial fistula is one of its rarest etiologies. We are presenting a case of pneumopericardium due to gastro-pericardial fistula secondary to gastric cancer presented with an inferior ST-elevation myocardial infarction (STEMI)-like picture.Our case is a 57-year-old male with a past medical history of metastatic gastric cancer status post chemotherapy and radiotherapy who presented to the emergency with acute onset severe burning chest pain with radiation to his back. He was diaphoretic, saturating 96% on room air, and hypotensive with a blood pressure of 80/50 mmHg, and his EKG showed sinus rhythm with a heart rate of 60 BPM and ST elevation in inferior leads meeting STEMI criteria.The patient was transferred for an emergency coronary angiogram with possible percutaneous intervention. Surprisingly, no significant lesions in his epicardial vessels would corroborate his clinical presentation and EKG changes. The decision was to obtain CT angiography to exclude aortic dissection and pulmonary embolism. His CT chest revealed a large pneumopericardium with a gastric-pericardial fistula.A nasogastric tube was placed with suctioning of gastric contents. Given his tamponade physiology, it was decided to do emergent pericardiocentesis draining only 20 cc of gastric contents and a significant amount of air. After the procedure, the patient was transferred to the ICU with stable hemodynamics. The case was discussed with surgery, but given his inoperable cancer, a palliative team was involved. Acknowledging his very poor prognosis, the patient requested discharge to home with home hospice.As reported in the literature, pneumopericardium is rare, and gastro-pericardial fistula associated with gastric cancer is even rarer. Clinical presentation is variable and can be confusing. Providers should be aware of how a patient with gastric cancer can be complicated with pneumopericardium, and they should have a lower threshold of suspicion in patients having risk factors. CT scan is the most sensitive tool for diagnosis.