Quercus humboldtii is an evergreen tree which grows to a height of 25 metres (82 feet) and a diameter of 1 m (3 ft 3 in), with buttresses of up to 1 m. Its bark is reddish gray or gray and fissured, breaking into squares and flaking.

The leaves are simple, alternate and lanceolate, up to 10–20 centimetres (4–8 inches) long, and clustered at the ends of the branches.

The fruit is a light brown, ovoid capsule, or acorn, with a leathery pericarp, 20–25 millimetres (3⁄4–1 inch) in diameter and 50–70 mm (2–2+3⁄4 in) long, resting on a scaly cupule.

Only one fruit per cupule is developed, and the inside of the acorn shell is woolly.

It is found on all three Colombian Andean mountain ranges and some lowland inter-Andean regions,[6][7][8] and in the Serranía del Darién on the border between Panama and Colombia.