The bar-throated apalis is a slender bird with a long tail and is 11 to 13 cm in length.

The plumage varies depending on the subspecies: the upper parts can be grey or green while the underparts are white or pale yellow.

All forms have a narrow black band across the breast, white outer tail-feathers and a pale eye.

Pairs sing a duetting song with the female's call being higher-pitched than that of the male.

This species forages for caterpillars and other insects amongst vegetation, often forming mixed-species flocks with other birds.