This species was first described in 1883 by Edward Meyrick using material collected by him on Ben Lomond near Lake Wakatipu in December.

Forewings moderate, costa straight, hindmargin rounded; dark fuscous, densely and finely strewn with yellowish and a few whitish scales; a curved cloudy whitish line towards base, anteriorly blackish-margined; a slightly bent whitish line at 1⁄3, posteriorly blackish-margined; sometimes a small blackish discal dot, and slender curved median line; a clearly marked white line beyond middle, anteriorly strongly blackish-margined, shortly and obtusely angulated in middle, and inner margin shortly toothed above and below middle; an irregular sinuate subdentate whitish-yellowish subterminal line: cilia with basal half dark grey, apical half sharply barred with dark fuscous and white.

Hindwings somewhat elongate, hindmargin rounded; dark fuscous; basal half irrorated with pale yellowish; a very obscure curved whitish shade before middle; a well-defined strongly-curved white median line; a very irregular subdentate whitish-yellowish subterminal line; cilia as in forewings.[3]N.

[3][6][13] This moth species prefers to live in high alpine habitat and has been found amongst grass and in herbfields.

[3][12] The host plants for the larvae of N. paradelpha are the endemic species in the genera Kelleria and Pimelea including Pimelia oreophila.