Proteus species belong to the Enterobacteriaceae family and are gram-negative-rods, commonly known to cause urinary tract infections and asymptomatic bacteriuria in elderly patients with risk factors such as diabetes mellitus and urinary catheterization. However, Proteus species are rarely known to cause infective endocarditis. We present a case of an 85-year-old female who presented due to decreased responsiveness with urine and blood cultures growing Proteus mirabilis. While she was being treated for her urinary tract infection, her echocardiogram showed vegetation on the left coronary cusp of the aortic valve and left pulmonic valve leaflet. Uncontrolled tachyarrhythmias and new-onset atrial fibrillation complicated the hospital course. Later, she became bradycardic during the hospital stay, and all rate-control medications were held. Unfortunately, she went into cardiac arrest and spontaneous circulation could not be established with resuscitation attempts and she expired. To our knowledge, this is a rare case of native valve infective endocarditis secondary to Proteus mirabilis, leading to uncontrolled tachyarrhythmias and death.