Mahonia is very distinctive in the form of its foliage and stems. The evergreen leaves are divided into two matching rows of leaflets, each leaflet defended by small spines, resembling holly leaves. The number of leaflets on each leaf varies according to species, some have nine or 13 leaflets, some with 19, and one species has 41 leaflets, giving it an almost fish bone-like look.

The number of leaflets is always an odd number, because there is a single leaflet at the tip of the leaves. The leaves are carried in rounded rosettes at the top of the stems, like a flat shuttlecock shape.