Schiedea viscosa is a weakly climbing or sprawling vine with stems often swollen at the nodes and terete (cylindrical), featuring a 4-angled or ridged structure. The primary stems can grow up to 50 cm long, with lateral branches nearly as developed and usually extending several nodes below the inflorescence. The leaves are simple and opposite, with narrowly elliptic to narrowly ovate-elliptic blades measuring 2.5 to 5 cm in length and 0.8 to 1.8 cm in width. The apex is mucronate, and the leaf bases are often connate around the stem. The leaf surfaces are moderately puberulent, with hairs that are gland-tipped (making the plant viscid) or not. The leaves are dark green with a purple tinge, thin, and membranous. The margins are entire and inconspicuously serrulate, particularly in the distal half, with 3 principal veins. The petioles are 0.4 to 0.8 cm long, weakly to conspicuously connate around the stem. Stipules are absent. The inflorescence is pseudoaxillary, usually bearing 1 to 11 flowers. All parts of the inflorescence are moderately puberulent, with hairs that may or may not be gland-tipped. Bracts are 7 to 20 mm long and foliaceous; peduncles range from 13 to 35 mm long, and pedicels are thinner, measuring 4 to 15 mm long. The flowers are bisexual (perfect), pendent, and seemingly adapted for bird pollination. The calyx has (4)5 sepals, 6.5 to 9 mm long, enlarging to about 12 mm in fruit. The corolla (petals) is absent. There are 10 to 13 stamens with 4.2 to 5 mm long filaments and pale reddish-purple anthers. The superior ovary is 1-celled, with free-central ovule placentation and 5 to 8 styles. The fruit is a narrowly ovoid capsule, 8 to 12 mm long, enclosed by or exserted from the persistent dried calyx. Seeds are relatively few to numerous, approximately 1.0 mm long, black, and released as the capsule gradually rots. It grows in diverse mesic forests or on the margins of wet forests, typically dominated by Acacia koa and Metrosideros polymorpha with Alyxia stellata, between 610-1150 meters.