The black-breasted weaver was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae.

In the non-breeding male and female, the crown is brown like the rest of the upperpart plumage, and the black pectoral band is less developed.

Flocks frequent cultivation and the reedy margins of tanks and jheels (shallow lakes), or extensive tall grass areas.

He flaps his wings deliberately and sings softly tsi-tsisik-tsisik-tsik-tsik, like the chirp of a cricket or the subdued squeaking of an unoiled bicycle wheel.

Built in reed-beds in marsh, often moonj or kans (Saccharum spontaneum), with some of the growing reeds incorporated into the dome as support.

At the 'helmet' stage of construction a quantity of wet mud or cowdung is daubed thickly along the edge, with bright coloured scarlet or orange flowers or flower petals (Lantana, Lagerstroemia) incorporated; observations suggest that this is part of the courtship rituals and exercise a direct influence on the reactions of the visiting female, both for this species and the streaked weaver.