The present invention is directed to antagonistic antibodies and antigen binding fragments thereof having binding specificity for PACAP. These antibodies inhibit, block or neutralize at least one biological effect associated with PACAP, e.g., vasodilation. In exemplary embodiments these antibodies and antigen binding fragments thereof may comprise specific VH, VL, and CDR polypeptides described herein. In some embodiments these antibodies and antigen binding fragments thereof bind to and/or compete for binding to specific epitope(s) on human PACAP. The invention is further directed to using these antagonistic anti-PACAP antibodies, and binding fragments thereof, for the diagnosis, assessment, and treatment of diseases and disorders associated with PACAP and conditions where antagonism of PACAP-related activities, such as vasodilation, mast cell degranulation, and/or neuronal activation, are therapeutically beneficial, e.g., headache and migraine indications.