Presented here is the case of an immunocompetent pregnant woman with probable cytomegalovirus encephalitis. The clinical picture was characterized by diffuse headache, drowsiness and the development of an acute confused state. Diagnosis was based on the documentation of recent cytomegalovirus seroconversion with low avidity for the immunoglobulin G class antibodies. Initially, the diagnosis of encephalitis was challenging due to the subtle findings in cerebrospinal fluid and the normal electroencephalograph results. However, repeated tests revealed findings compatible with the diagnosis of encephalitis. Due to the suspicion of herpes simplex encephalitis the patient was treated with acyclovir. Within a few days rapid resolution of the fever and complete recovery were observed. Cytomegalovirus encephalitis should be considered early in the evaluation of pregnant women if appropriate clinical symptoms are present.