We report a case of almost 9-year survival of a patient with unresected gastric cancer with peritoneal metastasis. A 76-year-old Japanese man was admitted to the hospital for resection of gastric cancer, but it was not resected because of peritoneal metastasis. After discharge, the patient was treated with combination chemotherapy of S-1 and paclitaxel (PTX). After 8 cycles of chemotherapy, the tumor disappeared. We recommended surgical therapy, but he did not agree. The chemotherapy was continued for almost 9 years with 8 regimens including S-1 plus PTX (21+8+5 cycles), S-1 plus CPT-11 (11+2 cycles), S-1 plus docetaxel (DOC) (25 cycles), S-1 plus CDDP plus trastuzumab (1 cycle), PTX (5 cycles), PTX plus trastuzumab (1 cycle), DOC (6 cycles), and nab-PTX (1 cycle). With nutrition support provided through an enterocutaneous fistula and home parenteral nutrition, he has taken chemotherapy throughout without severe complications.