Deltoplastis tetradelta is a moth in the Lecithoceridae family. It was described by Meyrick in 1906. It is found in Sri Lanka. The wingspan is about 20 mm. The forewings are pale greyish-ochreous suffused with ochreous-whitish. The base of the costa, and an oblique costal strigula before the middle are dark fuscous and there is a triangular dark fuscous blotch, edged with ochreous-whitish, extending on the dorsum from one-fifth to beyond the middle, and reaching three-fourths across the wing. There is a similar blotch extending along the costa from the middle to four-fifths, and nearly reaching to the dorsum, as well as a fine dark fuscous terminal line, shortly continued and stronger above the apex. The hindwings are light fuscous.