A large (4.0-5.0 cm wingspan) heavy-bodied grey moth. The body is slate grey or blackish. Forewings are dark grey or black over the basal half, shading to lighter grey on the outer half, and are crossed by a network of fine broken black lines. The hindwings are thinly scaled and somewhat translucent white, with a very fine network of indistinct dark lines and a narrow black terminal line. Antennae are narrowly bipectinate in males, finely serrate in females. Sexes similar except for size, with females larger than males. The two-tone forewing with dark basal half and the pale hindwings will separate the Poplar Carpenterworm from the similar Carpenterworm (P. robiniae) and Aspen Carpenterworm (A. populi).