A 71-year-old woman receiving CAR T-cell therapy for lymphoma developed a rare fungal lung infection caused by Schizophyllum commune six months after treatment. The infection presented similarly to other fungal diseases affecting the lungs and was diagnosed through bronchoscopy and fungal culture despite negative blood antibody tests. Standard antifungal medication (voriconazole) taken by mouth for four months completely resolved the infection, highlighting the need to consider rare fungi in patients receiving advanced cancer immunotherapies.