An 8-month-old neutered male outdoor cat was brought to our surgical center for a sudden onset of diarrhea, pyrexia, and lethargy. Physical examination revealed a loud left parasternal systolic murmur with no thrill. An echocardiogram showed a large hyperechoic vegetation (about 9 mm thick) on the aortic valve leaflets. The results of Doppler ultrasound examination were compatible with severe aortic stenosis. A singular urine culture test performed by cystocentesis samples enabled the isolation of more than 105 CFU/ml in a pure culture of Salmonella typhimurium. Enlarged mesenteric lymph nodes and moderate dilatation of small bowel loops were found on abdominal ultrasound examination. The patient was treated with marbofloxacin (2 mg/kg IM every 24 hours), cefazoline (20 mg/kg SC every 12 hours), metronidazole (10 mg/Kg IV every 12 hours), clopidogrel (18.75 mg PO every 24 hours), atenolol (0.5 mg/kg OS every 12 hours), and fluid therapy (ringer acetate 2.5 ml/kg/h), but after three days in hospital the patient died from presumed septic shock. A urine culture revealed that Salmonella typhimurium was sensitive to third generation cephalosporins but not to fluoroquinolones. Necropsy, histologic examinations, culture of the aortic valve, and PCR analysis of the aortic valve leaflets were eventually performed and Salmonella typhimurium endocarditis with myocardial phlegmon was confirmed. Endocarditis is a rare disease in cats and poorly described in the veterinary literature. To the best of the authors' knowledge, this is the first report of Salmonella typhimurium endocarditis and myocarditis in a cat.