In October 2012, a man in his 60s was hospitalized for the examination of ascites, and was diagnosed with gastric cancer and carcinomatous peritonitis. S-1+cisplatin (CDDP) therapy was administered as neoadjuvant chemotherapy; however, during therapy, he developed cerebral infarction. We suspected that the cerebral infarction was caused by a coagulation disorder owing to Trousseau's syndrome. After completing 5 courses of chemotherapy, total gastrectomy was performed. Thereafter, the treatment was changed to S-1+docetaxel(DTX), followed by nab-paclitaxel (PTX). Although cerebral infarction did not relapse after the administration of an anticoagulant agent, the patient died of gastric cancer 1 year and 5 months after the operation. Trousseau's syndrome is a coagulation disorder in cancer patients. Cerebral infarctions caused by Trousseau's syndrome have a high tendency to relapse, and the prognosis is poor. This syndrome should be kept in mind when treating cancer patients.