Background <p>Thoracic involvement is a rare extrapelvic manifestation of endometriosis. Due to the presence of endometrial‑like tissue within the thoracic cavity, cyclical respiratory or shoulder symptoms can occur. Owing to nonspecific features and limited yield of thoracic biopsies, diagnosis is often delayed. A high level of clinical suspicion is necessary to establish a diagnosis.</p> Case <p>A 44-year-old multiparous woman with a prior history of umbilical endometriosis presented with cyclical right-sided shoulder pain and dyspnoea. Imaging revealed haemorrhagic right-sided pleural effusion, small endometriotic cyst and moderate ascites. Extensive evaluation excluded tuberculosis, other infective pathology and malignancy. Pleural fluid analysis showed an exudative effusion with haemosiderophages, but no atypical cells. Considering the cyclical nature of symptoms, prior extrapelvic endometriosis, supportive imaging findings, and exclusion of alternative diagnoses, thoracic involvement related to endometriosis was suspected. Initial management with pleural drainage and hormonal suppression using a gonadotropin-releasing hormone agonist followed by dienogest resulted in clinical and radiological improvement of chest symptoms. So, video-assisted thoracoscopic surgery was not pursued. Definitive surgical management with total laparoscopic hysterectomy and bilateral salpingo-oophorectomy was done later. Intraoperative findings revealed extensive pelvic and peritoneal endometriotic deposits. Postoperatively, there was complete resolution of pleural effusion and ascites, and the patient has remained asymptomatic for over one year of follow-up.</p> Conclusion <p>Thoracic involvement should be considered in women with a history of endometriosis presenting with cyclical thoracic or shoulder symptoms and pleural effusion. A multidisciplinary approach and individualized medical and surgical management can achieve sustained symptom resolution.</p>