Gladiolus papilio is a deciduous, summer-growing, cormous geophyte, 500–750 mm in height. The corms are small and covered with brown tunics. The stems are erect and inclined after the uppermost leaf. The leaves are fan-like in appearance, the texture is firm and the veins are parallel. The leaves are sword-shaped and the midrib and margin are thickened, a characteristic of the genus. The shape of the leaf is lanceolate (tapering). A plant produces 6 or 7 leaves, but may produce up to 9 leaves, with a diameter of 9–14 mm. The lower leaves are the longest and they reach the middle of the stem, whereas the upper leaves are cauline (attached to the stem). Stems are slightly inclined. Cataphylls (scale like leaves) are leathery. Bracts are grey-green.

The inflorescence (the part of the plant that bears flowers) is a spike of 4 to 8 flowers, however, one can bear up to 13 flowers. The inflorescence is inclined towards the ground. The flowers are funnel- or bell-shaped, 18–20 mm long and are curved and drooping towards the ground. These nodding flowers make this species unique. The shape of the tepals is obovoid. In this species the flower colour is variable, flowers are often mauve or pinkish, sometimes creamy yellow or light green. A light purple or creamy green colour occurs on the inside of the upper tepals and a grey-purple colour occurs on the reverse. The inside of the lower lateral tepals have purple blotches with a yellow crescent. These patterns are nectar guides, which attract pollinators. Flowering time is from late spring through summer, from November to February. The fruit capsules are oblong and have 3 lobes, 18–24 mm in length. Seeds are winged and rust-brown.