Elsberg syndrome is a rare but well-defined clinical condition, including acute or subacute lumbosacral meningoradiculitis, which might be accompanied by myelitis and is often associated with herpes simplex virus type 2 (HSV-2) infection. We report the case of an immunocompetent 24-year-old man who presented with perineal pain, saddle hypoesthesia, and urinary retention associated with Elsberg syndrome due to HSV-2 infection 20-day after the posterior lumbar spinal fusion surgery. Lumbar magnetic resonance imaging (MRI) with gadolinium enhancement showed mildly enhanced and swollen right sacral nerve roots. One week after the admission, electromyography and nerve conduction studies (EMG-NCS) demonstrated severe axonal damage and radiculopathy at right S3 and S4 roots. Cerebrospinal fluid (CSF) analysis revealed lymphocytic pleocytosis, elevated protein, positive HSV-2 IgG index, and positive HSV-2 polymerase chain reaction (PCR). The patient was treated with intravenous acyclovir for 14 days and showed a gradual improvement in anal sphincter control and urination. Therefore, according to our findings, surgery might have an immunosuppressing role, and in cases with symptoms of cauda equina syndrome (CES) and systemic infection, in the postoperative setting, viral meningoradiculitis should be considered.