We report a patient with psoriasis who developed Mycobacterium marinum (M. marinum) infection after seven years of treatment with adalimumab, a human anti-TNF (tumor necrosis factor) monoclonal antibody. TNF is a pro-inflammatory cytokine that plays a central role in the pathogenesis of psoriasis and a number of other immune-mediated inflammatory diseases. TNF plays an important role in granuloma formation and host defense against mycobacterial infections. Several cases of atypical mycobacterial infections in patients on TNF inhibitors have been reported. To our knowledge, this is the second reported case of M. marinum infection in a patient on adalimumab for the treatment of psoriasis.