A 35-year-old man presented with a two day history of epigastric pain and was diagnosed with acute pancreatitis. During his workup, he was found to have a left-sided bilious pleural effusion. Further studies were unrevealing for an anatomic source. A bilious pleural effusion, almost always seen on the right side, is a rarity in clinical medicine and is usually secondary to traumatic injury. We report a case of an even more rare spontaneous, left-sided bilious pleural effusion.