Here, we report 2 patients with gastric cancer and peritoneal dissemination who were successfully treated with chemotherapy after undergoing treatment for an oncologic emergency caused by peritoneal dissemination. Case 1 involved obstruction of the sigmoid colon caused by peritoneal dissemination. After urgent colostomy, S-1/IP IV paclitaxel chemotherapy was introduced. The patient continued the therapy for 2 years and 2 months. Case 2 involved acute renal failure due to bilateral ureter obstruction and obstructive jaundice caused by peritoneal dissemination. This patient underwent emergency treatment consisting of Double-J ureteral stent insertion and endoscopic nasobiliary drainage. He was successfully started on chemotherapy with S-1/oxaliplatin/IP paclitaxel. He continued the therapy for 8 months without symptoms. Aggressive treatment might be effective for advanced gastric cancer showing oncologic emergency.