Over the past decade, an increasing number of opportunistic mycelial fungal infections have been reported in immunocompromised patients. Presented here is the first reported case of Microascus trigonosporus pneumonia, which occurred in a 24-year-old-man with a history of allogenic bone marrow transplantation with graft-versus-host disease. Despite the administration of effective antifungal treatment, the patient died after uncontrollable respiratory failure and multiorgan failure developed. This report confirms the results of previous studies that suggested a very poor outcome for bone marrow transplant recipients with non-Aspergillus mould infections.