Ceratotheca triloba is an annual, but some plants may last for a few seasons, albeit with reduced vigour. It branches from the base to develop a rounded shape with erect stems up to 2 m tall. The leaves are light green, slightly hairy, opposite, three-lobed and roughly toothed.
The flowers growing in racemes are spaced singly in leaf axils on the long, sometimes hairy stems. Flower colour is white or pale pinkish mauve. The stems are purplish on plants with mauve flowers and pale green when the flowers are white.
Each flower has a pointy calyx and green axillary bracts behind the large pendulous, tubular and lobed corolla. This corolla has a purplish striped lower lip that hangs down on the stem side of the flower. The flowering season is long, lasting from late spring through autumn, only a few flowers being open at a time.
The fruit is a hairy capsule borne erectly with two prominent horns at its tip. It becomes 2,5 cm long. When the fruit dries it releases small, flat, black seeds (Van Wyk and Malan, 1997; Pooley, 1998).