A 50-year-old woman was diagnosed with ascending colon cancer with bilateral ovarian metastases, carcinomatous peritonitis, and carcinomatous pleurisy. Nine courses of mFOLFOX6 treatment resulted in the disappearance of her ascites and pleural effusion and a marked decrease in her serum CEA and CA19-9 levels. Additionally, the primary tumor and ovarian metastases became smaller. Therefore, a right hemicolectomy with D3 lymph node dissection, total hysterectomy, and bilateral salpingo-oophorectomy were performed. Postoperatively, we changed the chemotherapy from mFOLFOX6 to bevacizumab+FOLFIRI because the patient had an allergic reaction to oxaliplatin, and we suspected lung metastasis. Because the lung metastasis grew after ten courses of bevacizumab+FOLFIRI, we changed to cetuximab+FOLFIRI. Unfortunately, 28 months after her diagnosis, the patient died of carcinomatous pleurisy.