We describe an outbreak of Mycobacterium chelonae infection in four young immunocompetent patients who were tattooed by the same artist. All had been previously tattooed without complication, but following the latest tattooing session, they all developed a very similar papular eruption confined to skin that had been newly coloured light grey. On histological examination of the eruption, granulomatous inflammation with microabscess formation was seen, in association with the tattoo pigment. Skin cultures grown under optimal conditions grew M. chelonae, sensitive to clarithromycin, from one patient. M. chelonae was also cultured from the contents and nozzle of an opened bottle of light-grey ink from the tattoo parlour frequented by the patients. Dermatologists should consider mycobacterial infection in patients who develop inflammatory changes within a new tattoo.