Intraductal papillary mucinous neoplasms (IPMNs) are a prevalent subtype of pancreatic cystic lesions, especially among individuals with liver cirrhosis. Intraductal papillary neoplasms of the bile duct (IPNBs) differ in histopathology based on the location and cellular variability in each location. Intrahepatic IPNBs are less aggressive than the extrahepatic variant, highlighting its heterogeneity and complexity. IPNBs are largely preinvasive but can develop into invasive carcinoma. Imaging typically reveals bile duct dilation with intraductal masses but may underestimate tumor burden. Intraductal ultrasonography and cholangioscopy are recommended for assessing the tumor extent, followed by biopsy. Surgical resection is the primary treatment for nonmetastatic IPNBs, with approaches varying based on the location and extent of the tumor. Liver transplantation with duodenopancreatectomy may be necessary for incomplete resections. This case describes a 76-year-old woman who presented with right upper quadrant pain. An abdominopelvic computed tomography (CT) revealed an ill-defined 4.4-cm mass in the left lobe of the liver. Endoscopic retrograde cholangiopancreatography (ERCP) revealed dilation in the left intrahepatic branches due to the mass, and fine-needle aspiration (FNA) showed adenomatous epithelium. Subsequent imaging identified persistent intrahepatic bile duct dilation, left lobe mass, and an abnormal porta hepatis lymph node, with FNA confirming an IPNB with low-grade dysplasia, but no metastasis to the lymph node. The patient underwent a left hepatectomy and portal lymphadenectomy. Surgical pathology confirmed IPNB without invasion. Postoperative ERCP showed no further lesions, and her cancer antigen 19-9 (CA 19-9) levels initially decreased but later began to rise. Positron emission tomography and CT imaging showed no evidence of malignancy, and she remains under continued surveillance due to persistently elevated CA 19-9 for nearly one and a half years. In patients with mass-related intrahepatic biliary dilation, IPNB should be considered in the differential diagnosis. This case provides valuable insights into the limited literature, highlighting the complexities of diagnosing and managing IPNB, a preinvasive lesion with malignant potential. Persistent elevated CA 19-9 levels following resection underscore the need for vigilant post-resection surveillance. The case emphasizes an individualized treatment approach and calls for further research to refine surveillance protocols and improve long-term outcomes, especially in atypical presentations or incomplete resections.