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The forewing is seven to nine millimetres and dark greyish brown with slight mottling. The antemedian line is indicated by a crisp white blotch along the inner margin, occasionally with an additional smaller spot towards the costa; while the postmedian line is also a crisp, fairly straight white line with a square blotch at the costa, though this line is sometimes incomplete. An additional slender cream blotch is present along the inner margin close to the base, but is sometimes obscured. In paler specimens, a dark streak is often visible through the middle of the wing from the base to nearly the outer margin. The fringe is brown and concolorous with the hindwing, which is brown. The labial palps are mottled black, grey, and white with the terminal portion faintly banded black and white. Much of the body and legs are black with white markings except for the brown abdomen. The Mompha unifasciella complex is similar but the pale markings along the inner margin of the forewing are infuscated with grey or other colours.

This is the main herbivore on Dwarf Fireweed in south-central Alaska (Doak 1991). Outbreaks have been observed in south-central Alaska, western British Columbia, and the southern Yukon (Doak 1991; Doak 1992). The larvae are leaf rollers on the shoots as soon as they emerge in the spring (Doak 1991). Adults are rarely collected, possibly because most Mompha have a peak flight period in the early morning and rarely come to lights (Koster & Sinev 2003).