Anti-IgLON5 encephalopathy is a new and rare autoimmune encephalitis with unclear pathophysiology. In this study, we reported an unusual case of anti-IgLON5 encephalopathy with concomitant herpes virus encephalitis. A 51-year-old man with HLA-DQB1*05:01 and HLA-DRB1*10:01, who suffered from an episode of acute encephalitis, mental disorders, and memory impairment was admitted to our hospital. Human alpha herpes virus 1, human gamma herpes virus 4 (Epstein-Barr virus), and IgLON5-IgG were detected in the cerebrospinal fluid, indicating anti-IgLON5 encephalopathy with concomitant herpes virus encephalitis of this patient. Brain magnetic resonance imaging revealed T2 hyperintensities in the left temporal lobe and enhancement in the hippocampus. A mild sleep disorder was also found by video polysomnography. The patient was then treated with antiviral drugs, intravenous immunoglobulins, methylprednisolone, and protein A immunoadsorption. After treatment, the patient’s clinical symptoms were partially improved. This is the first reported case of anti-IgLON5 encephalopathy with concomitant herpes virus encephalitis.