Key PointsQuestionWhat are the clinical characteristics and outcomes of patients withCutibacterium acnesendocarditis?FindingsIn this case series including 105 patients,C acnesendocarditis was seen predominantly among male patients with prosthetic heart valves and was characterized by absence of fever, close to normal inflammatory markers, and a prolonged time to positive blood culture results. Surgical treatment was required in a high proportion of patients.MeaningThis study suggests thatC acnesendocarditis is difficult to diagnose because typical endocarditis features are often absent; it is recommended to extend blood culturing for male patients with new-onset prosthetic valve dysfunction, peripheral embolization, or signs of heart failure.