Monoecious tree to 30m tall, to 0.8m d.b.h. at maturity; trunk straight. Crown In mature trees conical or columnar but open, apex rounded or pyramidal, sometimes wider than the lower crown. Bark to 2cm thick, exfoliating in horizontal strips, forming horizontal bands or flakes in the largest trees.
Leaves on mature trees of two kinds: adult and semi-juvenile. Adult leaves have a rhythmic variation in leaf size and spread along foliage branchlet; the size shape and range is ovate-broadly lanceolate, 5–10 × 3–6mm, apex incurved. Those on the penultimate branches shorter than or scarcely exceeding the diameter of their attachment base. Stomata on adult leaves on both surfaces, 10–14 discontinous rows each side of keel.
Male pollen-cones confined to higher parts on primary branches, terminal, initially erect but pendulous when shedding pollen. Cones cylindrical, initially straight becoming curved at maturity, 60–70 × 15–20mm. Female seed-cones terminal on short, stout foliage branches which widen below the cone, usually solitary, sometimes 2–3 together, erect. Mature cones green, subglobose, usually slightly longer than wide, 9–11 × 8–10cm., with a truncate apex. Seeds obovoid-oblong, 20–25 × 8–10mm, ripening light brown.
Araucaria biramulata has the unique combination of characters which include: adult leaves on the penultimate branches shorter than or scarcely exceeding the diameter of their attachment base; rhythmic variation in adult leaf size and spread along foliage branchlets; lateral extensions at the base of adult axis leaves absent. The most similar species are Araucaria bernieri, A. scopulorum and A. humboldtensis.