Yellow toadflax is an erect, herbaceous perennial typically growing numerous stems 1–3 ft (0.3–1 m) tall from a taproot with spreading lateral roots. Leaves are alternate, green, pointed at both ends, and may have small petiole-like stalks. Older leaves are narrow and typically 1–2 in (2½–5 cm) long with a large central vein on the underside. Flowers are pale yellow and snapdragon-like with an obvious upper and lower lip and a spur pointing downward. Each has a fuzzy, bright orange throat. Flowers occur in spiked clusters at the top of the stem. Each flower produces an oval capsule fruit holding 10–40 viable, flat, disc-shaped seeds.