Stenotrophomonas maltophilia is frequently isolated from hospital environments. In recent years, it has been reported that this bacterium is causing hospital infections at increasing rates and is gaining importance because of its multiple resistance. Although it has been related to several infections, endocarditis caused by S. maltophilia is rarely encountered. In this case study, endocarditis in a 40-y-old man with a history of aortic valve replacement is presented. Blood cultures revealed S. maltophilia to be the aetiological agent, which showed multiresistance to various antibiotics. Ticarcillin-clavulanate and trimethoprim-sulfamethoxazole were used in the treatment.