A 28-year-old pregnant woman at 26 weeks and 2 days gestation visited a local outpatient clinic complaining of a tender abdominal mass. Examinations revealed an advanced gastric cancer with multiple liver, bone, lymph node metastasis and mesenteric dissemination, thus she was transferred to our division at 27 weeks and 1 day-gestation. With her consent we decided to maintain her pregnancy until 28 weeks when the delivered fetus could be kept alive an incubator, avoiding the adverse effect on the fetus by anti-cancer chemotherapy to mother. Rapid fetus delivery by cesarean section was carried out at 28 weeks and 1 day gestation, yielding a 958-gram baby. The mother complained of respiratory distress and suffered from lymphangitis carcinomatosa on the 3 postoperative day. We began combination chemotherapy with S-1 and paclitaxel (S-1 100 mg/day, 3 weeks on, 2 weeks off and paclitaxel 70 mg/day on 1, 8 and 15) was started on the 4th postoperative day. Although temporary regression of lymphangitis carcinomatosa was seen with a relief of symptoms, her condition deteriorated on the 24th days. The second course chemotherapy was started on the 28th days without any relief of symptoms. Her general status deteriorated and she died on the 33rd postoperative day. The association of pregnancy and gastric cancer is rare but such cases are often in an advanced clinical stage, with bad prognosis. It is necessary to determine the treatment strategy on the basis of comprehensive consideration of the status of both the mother and fetus. Upper gastrointestinal endoscopy when gastric cancer is suspected is recommended in any pregnant woman with long-term morning sickness.