Laryngotracheobronchitis (LTB) is a common disease in the pediatric population, and it is rarely caused by a fungal infection. Acute respiratory failure caused by fungal LTB mainly occurs in immunocompromised patients, and early diagnosis is closely associated with morbidity and mortality. However, an appropriate diagnosis is challenging for pediatricians because symptoms and signs of LTB caused by Aspergillus spp. are nonspecific. Here, we report a case of progressive respiratory failure caused by pseudomembranous LTB in a child with a suspicion of primary immunodeficiency and highlight the importance of an early investigation, especially in immunocompromised patients.