Very similar to A. hypoleucus and its aedeagus is identical. Differs primarily in the shorter metatarsomeres (in males the first segment of the hind tarsus ('foot') is only about as long the next two segments combined) and in its usually more robust overall form.

Agrilus assimilis tends to occur in dryer areas than A. hypoleucus. There is evidence that it intergrades with A. hypoleucus. Some earlier museum collections that have been identified as A. hypoleucus are probably A. assimilis.

The type is from WA. Curletti 2001 placed a number of species in synonymy under this taxon including A. purpuratus (Syntype from Morialta, as 'Moriatta') described by Hope 1846b in the same paper as A. assimilis.

Turner 2001b noted the absence of specimens and records from the well-collected Sydney and eastern coastal areas and suggested that the species does not extend eastwards beyond the drier western side of the Great Dividing Range.

Like Agrilus hypoleucus, this species probably feeds mainly on Acacia foliage. Curletti 2001 reported it being collected from Acacia ligulata, A. pycnantha and Eucalyptus fasciculosa.