Backgrouond: Aggregatibacter aphrophilus (A. aphrophilus) is a gram negative, capnophilic, fermentative, coccobacillus that is occasionally isolated from patients with infective endocarditis. It has also been reported to cause brain abscess, empyema, meningitis, osteomyelitis and joint infection. Herein we report the first case of brain abscess caused by A. aphrophilus in Korea. Case: A 26-year-old man visited hospital for a headache during three weeks. He presented fever, nausea and vomiting for three days. His blood pressure was 108/69 mmHg and his body temperature was 36.9 ℃ at that time. His past medical history was unremarkable. Brain magnetic resonance imaging (MRI) was performed and revealed the 4 cm sized abscess in the frontal lobe with profound perilesional edema and subdural empyema. He received empirical intravenous antibiotic treatment with ceftriaxone 2.0 g every 12 hours, vancomycin 1.0 g every 12 hours and metronidazole 500 mg every 8 hours. On the 4th hospital day, he had decompressive craniectomy and drainage of the abscess. On the 8th hospital day, A. aphrophilus was identified in the culture of abscess. Vancomycin and metronidazole were discontinued and ceftriaxone monotherapy was maintained because it was susceptible to the 3rd generation cephalosporin. On the 11th hospital day, transthoracic echocardiography was performed, but there was no evidence of endocarditis. After a eight-week course of intravenous ceftriaxone therapy, follow-up MRI revealed almost resolved abscess. Intravenous ceftriaxone was changed to oral cefixime 100 mg every 12 hours and he was discharged. He treated with oral cefixime for 12 weeks in outpatient clinic until the complete resolution of brain abscess on MRI.