Temozolomide (TMZ) is a cytotoxic agent of the imidazotetrazine class, chemically related to dacarbazine. Its use poses higher risks of lymphopenia and opportunistic infections. Prophylaxis for Pneumocystis jiroveci must be considered up to 12 months after treatment discontinuation. The due literature (MEDLINE) makes no mention of a possible connection between the use of TMZ and tuberculosis (TB). A female patient, aged 59, featuring glioblastoma multiforme and having undergone solely a brain biopsy, was submitted to TMZ along with radiotherapy. After the first TMZ maintenance cycle, the referred patient was admitted displaying a background of a 40-day afternoon fever and productive coughing. She was thus submitted to a bronchoscopy and LBA, which resulted BAAR 1+/4+. TMZ was then suspended, and rifampicin, isoniazid, and pyrazinamide introduced. Considerations on prophylaxis with isoniazide in cancer patients are long-lived and scarce. Some subgroups are likely to benefit from the prophylactic administration of isoniazide during TMZ treatment, such as those patients under high doses of corticoids, patients with past medical history of TB, the malnourished, patients from endemic regions, and patients with highly reactive tuberculinic tests. That, nevertheless, must not restrict the administration of TMZ, but, rather, stand for a warning about its possible toxicity, and thus mitigate complications.