Key Clinical MessageA 31‐year‐old female with a diagnosis of bipolar disorder developed black hairy tongue after alprazolam therapy. Her symptom resolved 10 days after the cessation of alprazolam.AbstractAlprazolam is a widely used antidepressant and antianxiety drug. Mild to moderate side effect of alprazolam was commonly seen, including lethargy, dizziness, headache, dry mouth, nausea, fatigue, constipation, and blurred vision. In this case, we reported a patient developed black hairy tongue after alprazolam intake, and her symptom resolved after 10‐day discontinuation of alprazolam. This rare adverse event should be of concern to clinicians. This is the first paper to report an alprazolam‐induced BHT. This rare side effect of alprazolam should be concern of clinicians; we hope our report will promote the understand of BHT and acknowledge clinicians of this rare side effect of alprazolam.