Most posterior mediastinal malignancies in adults are of neurogenic origin. Accordingly, metastatic posterior mediastinal tumors are very rare. We report a case where a metastatic endometrial cancer developed in the posterior mediastinum and compress the lower trachea and both main bronchi. A 71-year-old woman who had received concurrent chemoradiation for stage IV endometrial cancer 13 years ago was admitted for progressive dyspnea. A 10 cm-sized posterior mediastinal tumor compressing the lower trachea and both main bronchi was found on the chest computed tomography. Positron tomography showed no metastasis to organs other than the posterior mediastinum. For pathologic confirmation, we performed bronchoscopy and EBUS-TBNA. After the procedure, the patient developed respiratory failure and received mechanical ventilation. The patient was diagnosed with metastatic endometrial adenocarcinoma based on pathologic findings (positive for p16 and TTF-1). She received concurrent chemoradiotherapy to treat metastatic endometrial cancer compressing the airways while receiving mechanical ventilator treatment. Thereafter, the patient can be successfully weaned from the ventilator. To the best of our knowledge, this is the first case in which previous endometrial cancer recurred as a posterior mediastinal tumor without the involvement of other abdominal organs or lungs. Although it is very rare, clinicians should be aware that metastatic cancer can manifest as a single posterior mediastinal tumor and can cause respiratory failure by compressing large airways.