Leukopenia and selective CD4+ lymphopenia represent major adverse events associated with the use of temozolomide (TMZ), an oral alkylating agent incorporated in the treatment of glioblastoma (GBM). The increased risk of opportunistic infections, including those caused by Pneumocystis jiroveci and cytomegalovirus, has been previously described in the literature. Here we report the case, the first to our knowledge, of a patient with pulmonary invasive aspergillosis immediately after the completion of chemoradiation with TMZ for GBM. Diagnosis was confirmed through a CT-guided lung biopsy, and the patient had excellent response to systemic voriconazole. This case illustrates that TMZ can be associated with severe opportunistic infections, presumably associated with T lymphocyte immune dysfunction, and patients exposed to this agent should be carefully monitored.