Ecosystems around the world have been degraded or destroyed by human activities, including regulation of river flows, clearance of vegetation, and removal of fallen timber. In southeastern Australia much of the original vegetation was converted to farmland. Remaining forests such as hilly box–ironbark and floodplain river red gum (Eucalyptus camaldulensis) are mostly regrowth. The yellow-footed antechinus (Antechinus flavipes) inhabits both types of forests and is the only small, native, carnivorous mammal on most floodplains in southeastern Australia. In this region, frequency of flooding has been reduced by regulation of river flows, which has led to decline in conditions favorable for flood-adapted terrestrial and aquatic organisms. Here, we compared numbers of A. flavipes in box–ironbark forests, and in river red gum forests that were deprived of floods; partially inundated with environmental flows; flooded naturally; and watered in large, artificial floods. We found that abundance of A. flavipes on floodplains and in box–ironbark forests increased with larger volumes of fallen timber and with greater numbers of large, old trees. In river red gum forests, numbers of 2nd-year females increased with proximity to flood locations. For conservation purposes, we recommend preservation of large trees, restoration of fallen timber on forest floors, and spring flooding of floodplains.