Gastric cancer during pregnancy is rare and the outcome is generally poor. A 36-year-old woman in the 28th week of gestation was complicated with disseminated intravascular coagulation (DIC), and she was diagnosed with gastric cancer with bone marrow metastasis. Cesarean delivery followed by sequential methotrexate (100 mg/m2) and 5-fluorouracil (600 mg/m2) chemotherapy was conducted. DIC was successfully managed with blood transfusion and chemotherapy. She has received chemotherapy in the outpatient clinic. This report is the second case of a pregnant woman with DIC as the initial manifestation of advanced gastric cancer. Prompt diagnosis and chemotherapy increases the chances of a relatively favorable outcome even in advanced gastric cancer presenting with DIC due to bone marrow involvement.