There seems to be some variation in views about whether this species is indigenous or naturalised! Both 'Flowers of the ACT (Wood) and Native trees of the ACT (NPA) mention that it may not be native. NSW Plantnet gives its range as all the areas surrounding the ACT, but it may be spreading by naturalising in the more southerly areas as it seems to have naturalised in many areas of Qld, SA, Vic and WA. Trees have existed on Farrer Ridge since well before the Parkcare group started in 1988.
Acacia decurrens appears to have spread from plantings undertaken within or adjacent to reserves. Its first record as occurring in the ACT is 1966. However it is natural in the ranges east of the Cullerin escarpment. There is a natural population at Brooks Hill (near Bugendore) and it occurs commonly near Tarago and points north and east from those sites