The role of immune checkpoint inhibitors (ICIs) continues to receive more attention as evidence emerges of their efficacy and improved survival in patients with advanced biliary tract malignancies including cholangiocarcinoma (CCA). In line with this evidence, we describe the case of a 52-year-old male patient who presented initially in October 2019 with abdominal pain. Investigations revealed multifocal hepatic masses that proved to be CCA that was considered unresectable. Chemotherapy with cisplatin (C) and gemcitabine (G) was initiated. In January 2020, progressive disease was noted, prompting the initiation of 5-fluorouracil (5-FU) and oxaliplatin along with pembrolizumab. Since March 2020, pembrolizumab monotherapy was pursued with radiological evidence of excellent response. Pembrolizumab monotherapy was continued through August 2022, where positron emission tomography (PET)/CT scan showed no evidence of active disease. This case serves to supplement the ongoing evidence of ICI efficacy especially as a durable, sustained radiological response was evident for more than three years from the time of diagnosis.