INTRODUCTION: Endoscopic retrograde cholangiopancreatography (ERCP) is an instrumental procedure in the diagnosis and management of pancreaticobiliary disorders. However, it is associated with risks of morbidity and mortality due to periprocedural complications. One of the most devastating complications is visceral perforation, and subsequently the development of pneumoperitoneum. Right pneumothorax is a rare post-ERCP complication, with a poorly understood underlying mechanism.Here, we report a case of isolated left pneumothorax. CASE PRESENTATION:The patient is an 89-year-old female who presented to the emergency department with shortness of breath and palpitations. The patient was hemodynamically stable, and physical exam was unremarkable. An electrocardiogram revealed accelerated atrial fibrillation. This prompted further work-up for pulmonary embolism and led to the incidental discovery of pneumobilia on computed tomography angiography (CTA). A subsequent computed tomography (CT) scan of the abdomen revealed gallstones in the common bile duct, and the patient was scheduled to undergo ECRP.