Science Progress, Volume 104, Issue 3, July September 2021. The revised World Health Organization guidelines on multidrug resistant tuberculosis include linezolid in the core drugs group. Consequently, the use of linezolid for patients with multidrug resistant tuberculosis is increasing. Common adverse events of long term linezolid use include bone marrow suppression and neuropathies. However, there is limited information on a rare adverse event, black hairy tongue. Here, we report a case of linezolid induced black hairy tongue in a patient with multidrug resistant tuberculosis. The etiology, pathogenesis, diagnosis, and treatment of black hairy tongue are also discussed.