The flowers of Aerangis mystacidii grow in multiple separate inflorescences, arising from below the leaves on peduncles sheathed at the base. A plant produces from two to six inflorescences, each having from 4 to 25 flowers. The arching to pendulous racemes seem not to branch, the stalk having a slight zigzag shape between the nodes where the long, reddish flower pedicels emerge. Racemes become 30 cm long.

The small flowers (about 2,3 cm in diameter), are resupinate, all the sepals and petals roughly elliptic to ovate. The lip (below) is biggest, the spur attached to it; the slightly oblique lateral petals are smaller than the sepals and reflexed. The thin, white spur with pink tinge is conspicuous, from 6 cm to 8 cm long and curving.

The flowers have a strong nocturnal, lily scent, maybe to interest moths. The fruit is a capsule. Flowering happens from late summer to early winter (Pooley, 1998; www.orchidspecies.com; www.africanorchids.dk).