The diamondback moth has a wingspan of about 15 mm and a body length of 6 mm. The forewings are narrow, brownish-gray and lighter along the anterior margin, with fine dark speckles. A creamy-coloured stripe with a wavy edge on the posterior margin is sometimes constricted to form one or more light-colored diamond shapes, which is the basis for the common name of this moth. The hindwings are narrow, pointed toward the apex and light gray, with a wide fringe. The tips of the wings can be seen to turn upward slightly when viewed from the side.