The species occurs in mulga and heath communities on sandhills and rocky ridges in all mainland states of Australia, except Victoria.

[3] Acacia brachystachya grows as a tall, bushy inland shrub to five metres with twisted, spreading stems, and is branched at the base.

[3] Acacia brachystachya of the families Fabaceae or Mimosaceae has been categorised as being part of the subfamily Mimosoideae.

[1] The species name Acacia brachystachya was coined in 1864 by George Bentham, an English man who never travelled to Australia but wrote Flora Australiensis.

[1] The type specimen, K000806612, was collected during the Bourke and Wills expedition in the Mutanie Ranges,[6] and came from Ferdinand von Mueller's herbarium.

[9] It has been concluded that it is likely that mulga plants are insect pollinated as this is often the case with arid zone Acacias.

[9] Because A. brachystachya is most easily distinguished from similar species by assessing the pods, it can be difficult to correctly identify without having experiencing the appropriate climatic conditions.