Here, we report a case of a brain abscess caused by two species of anaerobic periodontal pathogens. In June 20XX, a 45-year-old man visited a nearby clinic for weakness and abnormal sensation in the left arm. He was diagnosed with brain infarction based on head computed tomographic (CT) findings and was prescribed antiplatelet agents. However, he was subsequently referred to our department because of paralysis on the left side and underwent keyhole surgery to release the pus of a brain abscess which was diagnosed based on head magnetic resonance imaging findings. The identify of causal bacteria remains unknown in 30% of patients with an abscess due to anaerobic infection. Therefore, we collected multiple samples to identify the two species of anaerobic periodontal pathogens as the causal pathogens in the present case. The findings of this study suggest that the brain abscess was caused by a bacterial complex with a corn-cob structure that was transported to the cerebral cortex because of periodontal bacteremia in the patient, who had severe periodontal disease. Despite the difficulties in selecting antibiotics and deciding the method of administration, the outcome of a 14-week duration of postoperative antibiotics given with oral care and well-planned dental treatment was satisfactory.