Herpes simplex encephalitis (HSE) has been increasingly reported after neurosurgical procedures, mostly after tumor resections in patients with a prior history of HSE. Early detection and appropriate treatment are essential to prevent high mortality of the disease; however, there are diagnostic difficulties due to nonspecific prodromal symptoms. In addition, anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis has been reported after HSE as an immunological relapse. Here, we report a case of postherpetic anti-NMDAR encephalitis following right hemispherotomy for intractable startle-induced seizures, to emphasize the importance of early diagnosis and appropriate treatment. To our knowledge, this is the first reported case of anti-NMDAR encephalitis after postoperative HSE, and the third reported case of hemispherotomy as a curative treatment for startle epilepsy.