Aqueous synthetic wax dispersions which contain, as an essential component of the solid substance, a partially or completely neutralized copolymer of a C.sub.2 -C.sub.4 -olefin and an unsaturated mono- or dicarboxylic acid or dicarboxylic anhydride are prepared by neutralizing and dispersing the solid substance in an aqueous medium at above the melting point of the copolymer, by a method in which the processes of neutralization and of dispersion are carried out in one extruder or in a plurality of extruders connected in series.