It is a large
evergreen tree, reaching 40 m in height and 3 m in diameter. It possesses the mottled, shedding
bark that is characteristic of other
kauri species. Young trees are narrow and conic in shape, but begin to grow a wider, deeper
canopy after attaining a trunk diameter of 30–50 cm. In mature specimens, the
trunk is generally straight or slightly tapered and clear for 15–20 m before branching into a spreading canopy up to 35 m in diameter. The
root system is deep and strong, and the trees are highly wind resistant. The
leaves are green and glossy, elliptical to
lanceolate, 7–15 cm long and 2–4 cm wide. They are borne on short
petioles and held in a decussate pairs, but twisted so they lie in one plane. Leaves in the shade, of juvenile trees, and of individuals growing in wetter regions, tend to be larger. Male
cones of
A. macrophylla are elliptical and measure roughly 2–5 cm long at
pollen shed. The short pollen cones help distinguish this species from related
Agathis species. Female (seed) cones are globular, 8–13 cm across, and are borne on short
woody stalks. The majority of the cone crop matures early to mid February, as the cones turn brown and release the winged
seeds, which are small, flattened, and attached to a wing about 3.5 cm in length. Wind dispersal is very efficient; seeds have been known to travel tens of kilometres in the wind, and may even travel hundreds of kilometres during the
tropical cyclones that occur frequently in the species' range. ==Ecology==