Kingella kingae is a fastidious slow-growing gram-negative organism commonly found in the oral cavity. The organism is known to cause endocarditis with a long duration of symptoms (2 weeks to 6 months) before a diagnosis is made. The organism may take up to 6 days to grow in culture, delaying accurate microbiological diagnosis. K kingae–associated endocarditis has been well described with native valves but is rarely seen with prosthetic valves. We describe a case of prosthetic aortic valve K. kingae endocarditis and review other reported cases of prosthetic valve ENDO with this organism.