The leaves, which are in two rows, are darkish green, rough-looking and elliptical, and have notched edges. The underside of the leaf is covered with soft hairs.

The bark is dark brown, changing to a lighter brown and becoming hairy on the twigs. The inner bark is white, has a faint smell and contains mucilage which makes it "slippery". This inner bark has had many medicinal uses, including as a poultice for treating wounds by surgeons during the American Revolution.

The Slippery Elm flowers in April when the leaves begin to come out. The flowers are light green and are supported on the twigs by a very short stem (see photograph). The fruit is a samara ("key"), is light green, broad, almost round, and matures in the spring before the leaves are fully out. The Latin species name "rubra" refers to the buds, which are brown with rust-colored hairs.