Background. Aerococcus urinae was initially considered a commensal of the urinary tract, but there is now increasing evidence for its involvement in urinary tract and systemic infections. A. urinae endocarditis has a non-negligible mortality rate and occurs mainly in patients with underlying conditions or the presence of extraneous material. Case presentation. This report handles the case of a 65-year-old male with cardiac antecedents, who was admitted to the cardiology department after a syncope of unknown origin and diagnosed with severe mixed aortic valve disease and mitral valve sclerosis through the means of transoesophageal echocardiography (TEE). During hospitalization, the patient progressively deteriorated with the development of shortness of breath and an inflammatory syndrome. Both the urine and blood cultures showed growth of A. urinae. Treatment with piperacillin/tazobactam was started empirically. Repeated TEE showed evidence of endocarditis with vegetation and perforation of the mitral valve that required an emergency surgery with mitral valve repair. After surgery, gentamicin and penicillin G were administered for 48 h, followed by combined ceftriaxone/penicillin G treatment for 6 weeks. At first, flucloxacillin was also associated as the culture of the valve was negative. Finally, the 16S rRNA gene PCR on the valve tissue confirmed the A. urinae endocarditis. Conclusion. A. urinae is an underestimated cause of serious infections such as endocarditis. Urinary tract infections mainly in older men can be an entry point for this type of invasive infection.