The white-wedged piculet is long and weighs . Adult males of the nominate subspecies have a black cap with wide red tips on the forehead feathers and small white spots on the rest of the cap. Their face and hindneck are mostly white with a strong brown tinge and a white stripe behind the eye. Their upperparts are warm brown to grayish brown, sometimes with faint pale tips on the feathers. Their flight feathers are dark brown with narrow buffish white edges on the
secondaries and
tertials. Their tail is dark brown; the innermost pair of feather have mostly white inner webs and the outer two pairs have a wide white patch near the end. Their chin and throat feathers are pale buffish white with black edges that give a scaly appearance. Their underparts are mostly whitish with a pale buff wash; the breast has a scalloped appearance from black feather edges and the belly is plain or slightly streaked. Their iris is brown, the orbital ring grayish, the bill black with a paler base on the
mandible, and the legs gray to green-gray. Adult females are identical but for no red on the forehead. Juveniles are duller than adults and their underparts look more barred than scalloped. Subspecies
P. a. guttifer is larger than the nominate. It is usually darker, with more contrast on the face, more of a scalloped pattern on the upperparts, and warm buff underparts with wider black edges on the feathers. The male also has more red on the crown than the nominate. ==Distribution and habitat==