Pseudomembranous aspergillus tracheobronchitis is an uncommon form of invasive pulmonary aspergillosis, and it is generally seen in immunocompromised patients. We report about a mildly immunocompromised case with pseudomembranous aspergillus tracheobronchitis, which caused tracheal perforation, and Horner's syndrome. A 44-year-old female with uncontrolled diabetes mellitus, complaining of fever and dyspnea, was admitted to the hospital. She was hospitalized with community-acquired pneumonia and diabetic ketoacidosis. Insulin infusion and empirical antibiotics were firstly commenced. Bronchoscopy showed left vocal cord paralysis with extensive whitish exudative membranes covering the trachea and the main bronchi. Liposomal amphotericin B was added due to the probability of fungal etiology. Mucosal biopsy revealed aspergillus species. Second bronchoscopic examination demonstrated a large perforation in the tracheobronchial system. Despite all treatments, respiratory failure developed on the 25th day and the patient died within 2 days. Pseudomembranous aspergillus tracheobronchitis is fatal in about 78 % of all cases despite appropriate therapy. Early diagnosis and efficient antifungal therapy may improve the prognosis.