Penis morphology of 12 species of endemic New Guinean dasyurid marsupials, including the five currently recognized species of Murexia (M. habbema, M. melanurus, M. naso, M. longicaudata, and M. rothschildi); Phascolosorex dorsalis and Ph. doriae; Neophascogale lorentzii; and the four species of Myoictis (My. melas, My. wallacei, My. wavicus, and My. leucura), are described. Differences in form of the tip of the penis can be used to identify some of the species. The levator muscles are small in Murexia, Phascolosorex, and Neophascogale, and large in Myoictis. All species of Myoictis have accessory corpora cavernosa, which form an appendage to the penis. The anatomy of the penis of Myoictis spp. confirms a close relationship with the Australian dasyurid marsupial Parantechinus apicalis, as shown by a recent molecular study. Accessory corpora cavernosa appear to have arisen independently three times within the Dasyurinae.