Background: Hydatid cyst is a zoonosis rarely occurred except in endemic areas that capable of making pulmonary cavities fascilating fungus growth within it. Aspergillo-ma is a glob formed by hyphae from saprophyte growth of aspergillous specious in previously performed cavities within pulmonary parenchyma.

Case report: A 28 years old male patient without any comorbidity presented in emergency department with progressive two month dyspnea. Tube thoracostomy is done because of respiratory distress and massive hydropneumothorax. Thoracotomy and lobectomy is performed due to complicated hydatid cyst. Histopathologic investigation reveals hydatid cyst layers with fungal hyphae within it on granulomatous background.

Conclusion: Hydatid cyst with fungal contamination must be mentioned in differentials of dyspnea with lower segment lung cavities, especially in endemic areas. Thoracic CT scan with IV contrast can reveal fungus ball. Surgery is a treatment of choice and capitonage can be a prophylactic measure from secondary fungal infection in hydatid cyst surgery.