In Chile, the strain of the mumps virus used in the vaccine is Leningrad-Zagreb (L-Z). Although the relationship between meningitis and the L-Z strain remains controversial, most of the reported cases have shown a benign course without permanent neurological sequelae. We present a case of a patient who presented an aseptic meningitis three weeks after immunization with a mumps vaccine; and laboratory confirmation showed positive serum mumps IgM antibody. In this clinical case, there was a temporal relationship between vaccination and the onset of the mumps and subsequently the meningeal involvement; the immunoglobulin curve demonstrates acute infection after vaccination. Although it was not possible to isolate the virus in CSF, it is reasonable to attribute the picture to a post-vaccinal infection.