Endometriosis is a common condition in which endometrial cells and stroma are deposited in extrauterine sites. Its prevalence has been estimated to be 10% of reproductive age females. It is commonly found in the pelvis; however, it may be found in the abdomen, thorax, brain, or skin. Thoracic involvement is a relatively rare presentation of this common disease. Thoracic endometriosis commonly presents as pneumothorax in 73% of patients. A rarer presentation of thoracic endometriosis is hemothorax (<14%) or hemoptysis (7%). Thoracic endometriosis is an uncommon cause of a pleural effusion. We present a case of 28-year-old African American female with no other medical conditions. She presented to the hospital with worsening right-sided pleuritic chest pain, dyspnea, and menorrhagia. She had been complaining of pleuritic chest pain for 5 years, the onset of which corresponds to the start of her menstrual cycle and is relieved with cessation of menses. Initial laboratory studies revealed a severe microcytic anemia with normal coagulation profile. Chest X-ray showed small right pleural effusion and suspicious for airspace disease. A computed tomography (CT) of chest was ordered for further clarification and identified large right pleural effusion. CT-guided thoracentesis removed 500 ml of serosanguinous fluid consisting of blood elements. There can be multiple sites involved with endometriosis and can present with wide range of symptoms that occur periodically with menses in young woman. The history and pleural fluid findings of this case are suggestive of Thoracic Endometriosis Syndrome. The diagnosis of this is often missed or delayed by clinicians, which can result in recurrent hospitalization and other complications. As internists we should be suspicious of atypical presentations of endometriosis and treat them early before complications develop. This case also highlights the importance of suspecting atypical etiologies for pleural effusion.