Gardenia brighamii is a small tree up to 6 m (20 ft) in height. Trunks are up to 30.5 cm (12 in) in diameter and somewhat smooth. The shiny, dark green leaves are oval-shaped and measure from 2.2 to 10.5 cm (1 to 4 in) long and 1.5 to 5.5 cm (0.5 to 2 in) wide. The solitary flowers are white and very fragrant. The flowers range in size from 2.5 to 3.8 cm (1 to 1.5 in) in diameter. Fruits are hard, round, greenish, and moderate in size, about 3.8 cm (1.5 in) in diameter. The inside of the fruit is fleshy and contains many small seeds.