Asplenium milnei is a ground fern only found on Lord Howe Island.

[1] A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades,[2] which were given informal names pending further taxonomic study.

A. milnei belongs to the "Neottopteris clade",[3] members of which generally have somewhat leathery leaf tissue.

It forms a clade with A. pteridoides and A. surrogatum, two other Lord Howe Island endemics, suggesting that all three species diverged after a single colonization of the island by their ancestor.

[4] This clade is sister to a large group of Pacific Ocean spleenworts.