Ear ossicles were extracted from the skull of 64 specimens representing 31 marsupial species; all major extant marsupial clades were sampled except for Notoryctes. Images of ossicles were obtained using a scanning electron microscope and exported digitally to a graphic computer software. Thirteen characters and 31 character states were defined and coded to encompass the observed morphological variation. A composite phylogeny summarizing published molecular and morphological data was used to map the characters, revealing homoplasy in all three ossicles. The majority of transformations recorded occur between species, genera, or subfamilies, while few of them characterize higher-level taxa. The two alternative phylogenies of phalangeriforms being monophyletic or paraphyletic receive equal support from ossicle characters.