Gastric cancer with Virchow's lymph node metastasis (LNM) is not indicated for initial curative surgery. Although there have been some case reports of curative resections after pre-operative treatment, including immune checkpoint inhibitors (ICIs), there is no consensus regarding the optimal timing of surgery. We describe a rare case of initially unresectable gastric cancer treated preoperatively with nivolumab combined chemotherapy, which achieved a pathologically complete response. An 82-year-old man was referred for gastric cancer treatment. Contrast-enhanced computed tomography revealed stomach wall thickening and swollen left supraclavicular LN. This gastric cancer was assessed as unresectable due to the presence of Virchow's LNM; therefore, chemotherapy and ICI using S-1 plus oxaliplatin plus nivolumab were administered. After three courses of treatment, the primary tumor and Virchow's LN showed a marked reduction in size. The patient underwent Virchow's LNM resection as a preliminary step to determine indications for curative surgery. A pathological examination revealed no viable cancer cells were found inside the resected LN. The patient underwent distal gastrectomy. Pathological examination revealed complete degeneration of the primary tumor and regional LN without residual carcinoma. The patient did not receive adjuvant chemotherapy and survived with no evidence of recurrence for one year after the initial treatment.