Asplenium dielfalcatum, a member of the fern family (Aspleniaceae) grows from a rhizome (underground stern), 1 to 5 cm (0.4 to 2 in) long and 0.5 to 2 cm (0.2 to 0.8 in) in diameter that is covered with small black or maroon scales. Stalks of the fronds are dark brown to pale tan, usually have a dull surface, and are 1 to 7 cm in (0.4 to 2.8 in) long. The fronds are long and oval or straight in outline and 20 to 100 cm (8 to 40 in) tall by 2.5 to 9 cm () wide, with 12 to 45 divisions (pinnae) per side. The lower pinnae are small and rounded while pinnae farther up the frond are longer, undivided, and shaped like a sickle or a long triangle with veins forming a netted textured surface pattern. The sori are shaped like short lines 1 to 3 mm (0.04 to 0.1 in) long and are on low projections of the pinna margin.