Mycobacterium marinum is an atypical mycobacterium usually found in non-chlorinated water. It rarely disseminates, except in the setting of a severely immunosuppressed patient, and usually follows a sporotrichotic type of distribution. We report the case of a 45-year-old man who had ankylosing spondylitis and was receiving infliximab and isoniazid for latent tuberculosis. The patient presented with a 5-month history of painful erythematous and suppurative nodules and abscesses on the right upper extremity. M. marinum was not isolated in cultures and histologic findings together with clinical examination provided evidence of sporotrichoid-like fish tank granuloma. The patient was treated with rifampin (rifampicin) and ethambutol for 8 months and responded satisfactorily while continuing to receive infliximab. In accordance with data in the published literature, isoniazid proved ineffective in preventing M. marinum infection in this patient. While mycobacterial complications of tumor necrosis factor-alpha (TNFalpha) inhibitor therapy are well established, our case appears to be the first reported instance of M. marinum infection in a patient taking infliximab. As anti-TNFalpha agents become increasingly used for a variety of conditions, awareness of the potential infectious complications associated with use of these agents will be vital for clinicians.