After solid organ transplantation, patients are susceptible to infection caused by uncommon pathogens due the immunosuppressive drug therapy. Here, we report the first case of disseminated Mycobacterium genavense infection in a HIV seronegative renal transplant patient. The most striking clinical feature was a decreased consciousness. Blood results revealed hyperammonemia with otherwise normal liver function. Occurrence of hyperammonemia and massive M. genavense infection has not been reported before.