The flowers of Jamesbrittenia tenuifolia grow solitary from leaf axils near stem tips, forming racemes. The calyx is cup-shaped, its pointed lobes curving out. The thin, dark flower tube is hairy, becoming from 8 mm to 14 mm long and thicker towards its tip.
The corolla is purple to blue, rarely white or pink. Its colour is darker near the base of the five spreading lobes. These lobes are angular at their tips, a feature of Jamesbrittenia. Inside the throat the flower is yellow and there is sometimes a touch of white near the mouth.
The blooming season is mainly from midwinter to early autumn, but when conditions are good it continues all year round (Manning, 2007; Bond and Goldblatt, 1984).