The name red fir derives from the bark color of old trees.

The leaves are needle-like, 2–3.5 centimetres (3⁄4–1+1⁄2 in) long, glaucous blue-green above and below with strong stomatal bands, and an acute tip.

The cones are erect, 9–21 cm (3+1⁄2–8+1⁄4 in) long, yellow-green (occasionally purple), ripening brown and disintegrating to release the winged seeds in fall.

Red fir also tends to have the leaves less closely packed, with the shoot bark visible between the leaves, whereas the shoot is largely hidden in noble fir.

This tree was first recorded by William Lobb on his expedition to California of 1849–1853, having been overlooked previously by David Douglas.