We report 3 cases of advanced gastric cancer with peritoneal dissemination (PD) who underwent oophorectomy for ovarian metastases that occurred during chemotherapy. Case 1: The patient was a 43-year-old woman who had type 4 advanced gastric cancer with PD. After 24 courses of S-1 plus IV and IP paclitaxel (PTX) combination therapy, oophorectomy was performed for a rapidly growing left ovarian metastasis. Thirty-four months after the start of therapy, she has completed 44 courses of S-1 plus IV and IP PTX therapy and she is continuing the treatment. Case 2: The patient was a 77-year-old woman who underwent total gastrectomy with D2-#10 lymph node dissection and cholecystectomy for gastric cancer with PD. Right ovarian resection was performed for an ovarian metastasis 30 months after gastrectomy. She continues receiving chemotherapy 8 months after oophorectomy. Case 3: The patient was a 42-year-old woman who received S-1 plus CDDP combination therapy and 22 courses of S-1 plus IV and IP PTX for gastric cancer with PD, and oophorectomy for bilateral ovarian metastases was performed. After 10 courses of S-1 plus IV and IP PTX therapy, she died of cancer. We discuss the significance of oophorectomy during chemotherapy for advanced gastric cancer with PD.