Deinbollia oblongifolia is an erect sparsely-branched shrub or small slender tree, about 5 m tall. Leaves alternate, compound, large, 300-500 mm long. The leaf stalk is up to 90 mm long. Leaflets opposite, 5-10 pairs, oblong to elliptic, 35-150 x 15-50 mm, hard, pale green when new becoming dark green, with pale veins. Leaves with a few hairs or hairless.

Flowers are white to cream-coloured, 10 mm in diameter, densely packed in large terminal inflorescences up to 350 mm long, in autumn to early winter (May-June). The buds and flower stalks are covered in silvery or golden velvety hairs.

The fruit is a roundish fleshy berry, ± 10 mm in diameter, yellow when mature, hairy becoming smooth, and appear in winter to spring (June–October).

Seeds are up to 10 mm in diameter and are hairless.