Pellaea breweri grows from a branching reddish-brown rhizome covered in hairlike scales. Each leaf is up to 20 or 25 centimeters long. It is composed of a shiny brown rachis lined with widely spaced leaflets. The thick, pale green leaflets vary in shape from lance-shaped to diamond, triangular, or spade-shaped, and are sometimes divided deeply into lobes, or into two smaller leaflets. The edges of each segment are rolled under. The sporangia are located under the edges.