Biliothorax is the presence of bile in the pleural cavity. This condition is rare, and it usually results as a complication of hepatobiliary procedures. The authors present a case of an 87-year-old female who was admitted to the emergency department with the acute onset of severe dyspnea. A chest X-ray and CT revealed a large right-lung pleural effusion that, after thoracentesis, confirmed the presence of biliothorax. It is important to consider this entity when confronted with an effusion liquid of a dark greenish color, as a delay in diagnosis and management may be life-threatening.