Grasstrees (Xanthorrhoea) are an important structural component of many Australian ecosystems and also an important resource for many fauna species. Grasstrees have distinctive morphologies, with a crown of long thin leaves and skirts, the latter of which are accumulated dead leaves; both are incinerated by fire. This study determined the morphological features of Xanthorrhoea preissii, which change in response to fire from 6 months to 21 years post-burn. In addition, using radio-telemetry and spool-tracking, we determined that grasstrees are utilised as foraging and nesting resources for mardos (Antechinus flavipes leucogaster (Gray, 1841), Marsupialia: Dasyuridae). Recently burnt grasstrees (6 months post-burn) appeared not to be used by mardos at all. We found few mardos in these recently burnt sites, and the one individual we managed to track for 126 m utilised only a single grasstree: a 2-m-tall multiple-crowned grasstree that had escaped the fire was used as a nest site. For sites 5 years post-burn, mardos selectively utilised grasstrees with larger crown areas and those with a greater number of crowns compared with a random sample of available trees. At the 14-year post-burn sites, mardos still demonstrated some selection for grasstrees, although no specific single feature could be determined as most significant. We recorded humidity and temperature buffering effects in association with post-burn accumulation of grasstree skirt material and found that even dead grasstree ‘logs’ were an important resource for nests. We conclude that mardos utilise both live and dead grasstrees for foraging and nest sites, possibly owing to the availability of dense cover, a buffered microclimate, and potentially also food resources. Fire-management policies that promote habitat heterogeneity and retain several intact-skirted grasstrees within the landscape are likely to benefit mardos.