Colorectal cancer (CRC) most often metastasizes to the liver, lung, lymph nodes, and peritoneum; involvement of the gallbladder or extrahepatic biliary region is distinctly uncommon and can create diagnostic and therapeutic uncertainty. We report a 67-year-old woman with a history of treated left breast cancer who presented in April 2025 with hematochezia and anemia. Colonoscopy demonstrated a large obstructing ascending colon mass; biopsy confirmed adenocarcinoma. Staging PET-CT (June 2025) showed an FDG-avid right colonic mass with FDG-avid peri colonic and porta hepatis/portacaval nodal disease and no definite visceral organ uptake. Serum carcinoembryonic antigen (CEA) was markedly elevated (2690). She underwent laparoscopic right hemicolectomy with partial omentectomy (July 2025). Histopathology revealed an 8.5-cm moderately-to-poorly differentiated adenocarcinoma invading the visceral peritoneum (pT4a) with extensive nodal involvement (12/13 nodes; pN2b) and omental metastasis, consistent with stage IV disease. Multidisciplinary tumor board recommended systemic therapy; however, the patient initially declined chemotherapy. By late December 2025, rising symptoms and imaging demonstrated progressive retroperitoneal/mesenteric nodal and peritoneal disease and a new lytic C7 lesion. Before planned palliative chemotherapy, she developed obstructive jaundice with right upper quadrant pain (January 2026). CT and MRCP showed progressive intra-and-extrahepatic biliary dilatation and new marked diffuse duodenal wall thickening with mass effect at the ampulla, causing secondary biliary and pancreatic duct obstruction. She was managed with percutaneous transhepatic biliary drainage and subsequent endoscopic duodenal stenting to re-establish enteral intake. This case highlights the need to consider metastatic CRC in atypical biliary/duodenal obstruction patterns, to distinguish secondary involvement from a new primary periampullary process, and to use multidisciplinary palliation to enable systemic therapy when appropriate.