The flowers of Oncoba spinosa are solitary and terminal or axillary with a 1.5 cm long peduncle.
The calyx is 4-lobed. The sepals are orbicular and about 1 cm across. The calyx is light green and glabrous.
The corolla is composed of 2 verticils of 4 white-coloured and glabrous petals. The petals are obovate, about 2 cm long and 1.5 cm wide.
The androecium is composed of numerous stamens with 7-8 mm long filament and oblong and 1.5 mm long anther..
The style is stout and 3.5 mm long with a capitate stigma at the end.
The flowers are fragrant.