Background: Black Hairy tongue consists of a benign condition related to abnormal keratin build-up in filiform papillae, giving them an elongated hair-like appearance. We report a case of a 35 y/m presented who developed black discoloration of tongue while on linezolid therapy. Case Description: A 35 y/m, presented to gastroenterology OPD with chief complaints of on and off chromic discharging sinuses from port site right hypochondrium since past 1 y. Pus swabs taken from discharging site were taken and sent for gram stain, ZN stain and culture. Gram stain showed few pus cells,gram positive cocci in clusters. ZN stain showed few acid fast bacilli. Discussion: Bacterial culture grew MSSA and LJ media showed growth of rapidly growing mycobacteria(RGM) after 6 d of incubation. RGM was further identified by HAINS genotypic assay as Mycobacterium abscesses subspecies abscesses. Antibiotic susceptibility was performed on Middlebrook 7H11 with OADC and isolate was found to be sensitive to amikacin, gentamycin,imipenem and linezolid and resistance to macrolides, fluroquinolones and doxycycline. Diagnosis of MSSA and Mycobacterium abscesses infection was made and patient was started on amikacin and linezolid 600 mg OD. On 16thday of therapy patient developed dark discoloration of dorsum of tongue, teeth and oral mucosa. Other antibiotics, drugs, poor oral hygiene, smoking, and consumption of coffee or other coloured beverages were rule out as risk factors. Patient was switched on to meropenem and aminoglycoside. Discoloration improved after three weeks of discontinuing Linezolid. Conclusion: The diagnosis of BHT primarily relies on a visual intra- oral examination. Described adverse reaction is uncommonly described with prolonged Linezolid therapy.Careful review of known precipitating factors and recent medication changes is also fundamental in the diagnosis of BHT. Overall clinical prognosis of BHT is excellent.