Arctonoe fragilis's distribution ranges from the Alaska Peninsula south to Baja California. It is located in the low intertidal to 275 meters.  The most common place to find the scaleworm is in the ambulacral groove of the Mottled Star (Evasterias troschelii). Arctonoe fragilis can also be found on other species of six armed stars: (Leptasterias spp.),the Long-armed Sea Star (Orthasterias koehleri), the Black Sea Star (Stylasterias forreri), the Morning Sun Star (Solaster dawsoni) and others.