Background: Syphilis is an infectious disease caused by Treponema pallidum with multiple organ involvement in which the central nervous system (CNS) is also affected. Neurosyphilis should be considered in the differential diagnosis of many CNS infections due to its numerous various clinical manifestations. Hemiparesia and complex partial seizures are rare presentations of syphilis. Case Report: A 56 year old male patient was admitted to the emergency department due to fever, syncope and vomiting. His general condition was poor, he was somnolent and partially cooperative, and was disoriented in person and place. MRI resembled HSV encephalitis, mesial temporal syndromes; and increased mononuclear cells in cerebrospinal fluid (CSF) was suggestive for HSV encephalitis. However, CSF and blood tests supported the diagnosis of neurosyphilis. Conclusion: Neurosyphilis should not be overlooked at differential diagnosis in patients presenting with clinical and radiological findings suggestive of herpes encephalitis.