The swamp grass babbler occurs in the plains of the Brahmaputra and the Cachar district in the state of Assam, India, and in nearby parts of northern Bangladesh.

[2] Swamp grass babblers average 17 cm (6.7 in) long (big for a prinia).

There is a faint buff tint to the undertail coverts (but not the distinctive colouring for which the rufous-vented prinia is named).

The upper surface of the wings has barring formed by the covert feathers and their paler fringes.

They molt into adult head and body plumage, retaining their flight feathers, about 4 to 6 weeks after fledging.

[2] Calls include "a wheezy feez, and a quiet, very rapid nasal rattle."