Allocasuarina diminuta is a species of flowering plant in the family Casuarinaceae and is endemic to eastern New South Wales.

[2][3] Allocasuarina diminuta was first formally described in 1989 by Lawrie Johnson in the Flora of Australia from specimens collected by Karen Wilson near Conimbla National Park in 1982.

[4][5] The specific epithet, (diminuta) means "diminished", referring all its parts being smaller than those of the similar A.

[3] Subspecies annectens occurs between Sassafras, Braidwood and Lake Bathurst with a disjunct population south-west of Eden.

[7][8] Subspecies diminuta is found on the western slopes and nearby plains between Temora and the Pilliga forest, and as far east as Capertee and Bathurst.