Adult Wollemia nobilis trees are up to 40 metres (about 130 feet) tall, frequently becoming multistemmed with age, with dark reddish brown bark characterized by spongy nodules that give it a “bubbly” appearance. The resinous leaves of the fertile branches occur in four ranks and are up to 8 cm (about 3 inches) long, stiff, flattened, and narrowly strap-shaped; those of shade branches and juveniles are two-ranked, shorter, and narrower. The megasporangiate and microsporangiate cones occur singly on different branch tips toward the top of the same tree. The pendulous, slender microsporangiate cones can become 10 cm (4 inches) long and have numerous tiny pollen-bearing microsporophylls. The more massive, globose megasporophylls can reach 10–12 cm (4–4.7 inches) in diameter and appear somewhat spiny because the cone scales have outwardly curved elongate tips. A single cone may produce more than 300 small flattened winged seeds.

Soon after its discovery, W. nobilis became known as a living fossil. Pollen grains described in the genus Dilwynites are common in the fossil record of portions of Australia, New Zealand, Tasmania, and Antarctica dating back more than 90 million years to the Cretaceous Period and are virtually identical to those of the Wollemi pine. The trees that produced these pollen grains began disappearing from the fossil record within the last 10 million years when other species of Wollemia gradually became extinct. Leaf and cone fossil fragments stretching back to the Jurassic Period (200 to 145 million years ago) also bear a strong morphological resemblance to Wollemia. Thus, the recently discovered species represents a survivor of a group that was more widespread and diverse millions of years ago.