A 65-year-old man was admitted with left lower-limb cellulitis and an impending abscess. He was a known case of type 2 diabetes mellitus, with hemoglobin A1c (HbA1c) 7.6%, and was started on intravenous piperacillin-tazobactam. Wound debridement was carried out under local anesthesia. At admission, he had stage 1 acute kidney injury as per Kidney Disease: Improving Global Outcomes (KDIGO) criteria, which improved with supportive measures. On the 6th day of therapy, his relatives noticed a black discoloration over his tongue (Fig. 1). Examination revealed a dark coating confined to the dorsal surface of the tongue, with sparing of the tip and lateral borders. There was no associated pain or burning sensation. A diagnosis of black hairy tongue (BHT) was considered, possibly related to piperacillin-tazobactam. The antibiotic was discontinued, and the patient was advised to maintain good oral hygiene and to brush the tongue gently. The discoloration resolved completely within 1 week of these measures.