Artificial linear structures can cause habitat fragmentation by restricting movements of animals and altering home ranges. The negative impacts of these linear structures, especially of those other than roads, on arboreal species have been rarely studied even though these species can be greatly affected because of their fidelity to the canopy. We studied the home ranges of an endangered arboreal marsupial, the western ringtail possum (Pseudocheirus occidentalis), with a focus on the impacts of a road and an artificial waterway on their movement. We radiotracked 18 females and 19 males along a major road and an artificial waterway near Busselton, Western Australia, for 3 years and estimated home ranges using an a-local convex hull (a-LoCoH) estimator. No possum crossed the road successfully during the monitoring period while one crossed the waterway. Males had a mean home range size of 0.31 ± 0.044 (SE) ha, almost double that of the females at 0.16 ± 0.017 ha. Possums near the waterway had larger home ranges (0.30 ± 0.048 ha) than those near the road (0.19 ± 0.027 ha), and the size increased with proximity to the waterway, probably due to the greater availability of nearby canopy connections and the lower availability of preferable foliage. These results demonstrate that both the road and waterway represent significant physical barriers to possums, and the artificial waterway influenced home ranges more severely than the road. This suggests that linear infrastructure other than roads can affect movements of strictly arboreal animals, and negative impacts of these structures need to be assessed and mitigated by reconnecting their habitat, just as those of roads.