A 60-year-old man visited our hospital for further examination of an abnormal chest radiograph. Computed tomography (CT) images revealed enlarged mediastinal lymph nodes and multiple pulmonary nodules. Further evaluation by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) was performed and he was diagnosed with sarcoidosis. Six weeks after EBUS-TBNA, he presented to the emergency department with a high-grade fever. CT scan revealed an enlarged mediastinal lymph node. He was diagnosed with mediastinal adenitis and treated successfully with antibiotics. EBUS-TBNA is a highly accurate diagnostic tool, but clinicians should be aware of mediastinal infectious complication that could be asymptomatic for long period of time.