Thoracic endometriosis syndrome (TES) is an extremely rare disorder, and it is defined as the presence of functional endometrial tissue in pleura, airways, and lung parenchyma. We describe a rare case of a 29-year-old nulliparous female who presented with abdominal pain, dyspareunia, and shortness of breath. She complained of worsening of symptoms around the menstrual cycle. Initial workup showed markedly elevated CA-125 levels. A chest radiograph and CT of the chest, abdomen, and pelvis demonstrated large tension hydrothorax, ascites, and bilateral ovarian cysts. A chest tube was placed to decompress the tension hydrothorax, which drained copious amounts of blood. In view of the unexplained etiology of large hemothorax and elevated CA-125 levels, an MRI of the abdomen and pelvis was performed. This revealed advanced pelvic endometriosis, a right pleural nodule, and ipsilateral hydropneumothorax. Based on these findings, a diagnosis of TES was presumed. The patient was then referred to video-assisted thoracoscopy (VATS) and continuous estrogen suppression for optimal treatment. On early follow-up, she presented with recurrent hydropneumothorax, which was successfully managed with CT-guided chest tube placement and remained stable on further follow-ups. TES diagnosis is often challenging and delayed, demanding a high index of suspicion in patients with risk factors and characteristic clinical presentation. Radiologists should be aware of key imaging findings to help in early diagnosis for timely clinical and surgical management.