Surgical site infection (SSI) is an emerging problem in all fields of surgery, as well as in neurosurgery, with numerous strategies against SSI initiated in many countries. In this report, we describe a case of SSI caused by Neisseria subflava a month after ventriculostomy placement for acute hydrocephalus. A 53-year old man was referred to our hospital, and was diagnosed with a thalamic hemorrhage with ventricular rupture. Bilateral ventriculostomies were performed on the day of presentation. After intensive care for the acute stage, an SSI at the left ventriculostomy site was recognized on the 39th hospital day. The installed reservoir and ventricular tube was removed on the 40th hospital day. The CSF cell count was 2064/3, and N. subflava was recovered from the CSF culture. N. subflava is a common inhabitant found in the human upper respiratory tract, and is reported to be a rare cause of meningitis. There is one case report of meningitis caused by N. subflava transmitted during myelography from medical staff who did not wear facemasks during the procedure. Meningitis caused by N. subflava is rare, and transmission via a medical procedure is extremely rare. Although reported to be only rarely pathogenic, we must recognize that N. subflava can indeed be pathogenic, and can in rare cases be the cause of postoperative meningitis.