Patients with congenital varicella syndrome (CVS) typically present with clinical symptoms consisting of skin lesions, neurological defects, eye diseases, and/or limb hypoplasia. In rare cases, isolated manifestations in the brain or eye have been reported. The varicella-zoster virus (VZV), as the causative agent of CVS, could only be detected in a few infants with CVS. In addition, there is little in the literature on antiviral treatment of infants born with signs of CVS. We report a case of CVS in a male infant who presented with generalized clonic cerebral seizures at age 4 months. An endogenous intracerebral viral reactivation following intrauterine VZV infection was assumed. After the diagnosis was confirmed virologically, acyclovir was administered intravenously for 10 days and afterwards orally for 3 weeks. This antiviral treatment was aimed at preventing progression of the disease. We concluded from this case that infants with intrauterine VZV infection can suffer intracerebral VZV reactivations that require antiviral treatment.