A small, slim warbler with a long tail. Breeding males are distinctive, with gray upperparts contrasting with a puffy rufous throat and breast, and a bold white moustache mark. Female and non-breeding males resemble a washed-out version of the breeding male, with much less rufous below. Typically found in scrubby, dense bushy habitats, but also in more open woodland and savanna. Sings from the tops of bushes, giving a rattling and loud sequence of notes. The calls are dry “trkk” or "trk-tek" notes, which are also incorporated into the song. Very similar to Moltoni’s Warbler, and best separated by the call (single or subtly doubled notes rather than dry rattles); breeding male is also richer rufous below. Also very similar to Western Subalpine Warbler, but call is subtly different: Eastern’s is slightly softer and tends to have two syllables. Breeding males are separated visually from Western by having more white on the belly, a darker face, and a broader white moustache.