A 25-year-old female with no remarkable medical or family history presented with sudden chest pain and shortness of breath. Transesophageal echocardiography revealed a defect in intraventricular septum, and a loose mass image was observed on the septal cuspis of tricuspid valve. A total of 6 blood cultures were taken, one bottle of blood culture from each arm of the patient for three consecutive days. All bottles yielded growth of Neisseria animaloris. All isolates were identified by Phoenix (TM) 100 (Becton Dickinson, Diagnostic Instrument System, Sparks, MD, USA), and the identification was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonik, Bremen, Germany). Antibiotic susceptibility results were studied by gradient diffusion method, and interpreted as resistant to penicillin G and susceptible to ceftriaxone by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) 2013 standards for N. meningitidis. No risk factor such as animal contact or bite, and tooth or gum problems was detected in the patient evaluation because of the feature of the causative agent. Definitive infective endocarditis was diagnosed according to modified Duke criteria because of fever, infective endocarditis-prone cardiac condition and pulmonary embolism, vegetation in echocardiography and growth in consecutive blood cultures. Although there are some reports that N. animaloris causes wound infections in the cases bitten by a dog or a cat, there is no information about it as a causative agent for infective endocarditis. Our case is the only case of infective endocarditis that is caused by N. animaloris.