The two-volume set LNCS 11295 and 11296 constitutes the thoroughly refereed proceedings of the 25th International Conference on MultiMedia Modeling, MMM 2019, held in Thessaloniki, Greece, in January 2019. Of the 172 submitted full papers, 49 were selected for oral presentation and 47 for poster presentation; in addition, 6 demonstration papers, 5 industry papers, 6 workshop papers, and 6 papers for the Video Browser Showdown 2019 were accepted. All papers presented were carefully reviewed and selected from 204 submissions.