We describe a rare presentation of acute cardiac tamponade in a patient with gastric cancer in pregnancy. A 32-year-old woman developed dyspnea and tachycardia during the 28(th) week of her pregnancy. These symptoms were interpreted initially by the patient as a condition related to the normal state of pregnancy; however, her symptoms persisted over the next two weeks, and she was hospitalized for evaluation. The diagnostic work-up revealed metastatic gastric carcinoma to the pericardium associated with pericardial tamponade. Large pericardial and pleural effusions were the primary causes of her shortness of breath. Gastric cancer is very rare in pregnancy, and therefore may be not be suspected by physicians. Diagnosis may be further delayed because of overlapping symptoms occurring during normal pregnancy (nausea, vomiting, and shortness of breath). All these factors may contribute to a very high mortality of this malignancy during pregnancy.