Pallas's leaf warbler is one of the smallest warblers, with a large head and short tail.
At 9–10 centimetres (3.5–3.9 in) long and 4–7 grams (0.14–0.25 oz) in weight, it is slightly smaller than a yellow-browed warbler and barely any larger than a goldcrest.
It has greenish upperparts and white underparts, but is very striking, with prominent pale yellow double wingbars on the wing covert feathers, bold yellow supercilia and central crown stripe, and a lemon-yellow rump.
The bill is blackish-brown with a yellowish tinge to the cutting edges and the base of the lower mandible, the iris is brown, and the legs are brown with a green or greyish tinge.
Although the yellow rump is obvious when a bird is low in vegetation or hovering, it can otherwise be hard to see.

In Asia, Pallas's leaf warbler can be distinguished from its former subspecies by its yellower head stripes, wingbars and throat as well as its different vocalisations.
Other yellow-rumped Asiatic warblers resemble Pallas's; buff-barred and Brooks's leaf warblers are larger, much duller green above and less strongly marked, and their wing bars are buff and white respectively, not yellow.
Ashy-throated warbler has grey head markings, face and throat, and pale yellow underparts.

The sexes of Pallas's leaf warbler have similar plumage, but non-breeding birds are somewhat brighter green above and have broad, bright fringes to their flight feathers.
Juveniles are like the adults, but have a brown tinge to the upperparts, greyish-white underparts and a duller supercilium.
Adults have a complete post-breeding moult in August or September before migrating south.
Juveniles and pre-breeding adults have a partial moult in March or April, replacing all the body plumage and some tail feathers.

The song of Pallas's leaf warbler is delivered from a concealed perch near the top of a tall tree.
It is strong and prolonged, with a medley of whistles, tirrit-tirrt-tirrit-terchee-choo-choo-chee-chee-chee or similar, with some phrases reminiscent of a canary, and interspersed trills.
It lasts 2–4 seconds and may be heard in the winter quarters as well as from breeding birds.
The call is a short, soft dju-ee.
In contrast, the former subspecies have quite different songs, with sustained rattles for several seconds, or sometimes minutes.
Their calls are typically sharp and monosyllabic.
Pallas's leaf warbler is one of the smallest warblers, with a large head and short tail. At 9–10 centimetres (3.5–3.9 in) long and 4–7 grams (0.14–0.25 oz) in weight, it is slightly smaller than a yellow-browed warbler and barely any larger than a goldcrest. It has greenish upperparts and white underparts, but is very striking, with prominent pale yellow double wingbars on the wing covert feathers, bold yellow supercilia and central crown stripe, and a lemon-yellow rump. The bill is blackish-brown with a yellowish tinge to the cutting edges and the base of the lower mandible, the iris is brown, and the legs are brown with a green or greyish tinge. Although the yellow rump is obvious when a bird is low in vegetation or hovering, it can otherwise be hard to see.
In Asia, Pallas's leaf warbler can be distinguished from its former subspecies by its yellower head stripes, wingbars and throat as well as its different vocalisations. Other yellow-rumped Asiatic warblers resemble Pallas's; buff-barred and Brooks's leaf warblers are larger, much duller green above and less strongly marked, and their wing bars are buff and white respectively, not yellow. Ashy-throated warbler has grey head markings, face and throat, and pale yellow underparts.
The sexes of Pallas's leaf warbler have similar plumage, but non-breeding birds are somewhat brighter green above and have broad, bright fringes to their flight feathers. Juveniles are like the adults, but have a brown tinge to the upperparts, greyish-white underparts and a duller supercilium. Adults have a complete post-breeding moult in August or September before migrating south. Juveniles and pre-breeding adults have a partial moult in March or April, replacing all the body plumage and some tail feathers.
The song of Pallas's leaf warbler is delivered from a concealed perch near the top of a tall tree. It is strong and prolonged, with a medley of whistles, tirrit-tirrt-tirrit-terchee-choo-choo-chee-chee-chee or similar, with some phrases reminiscent of a canary, and interspersed trills. It lasts 2–4 seconds and may be heard in the winter quarters as well as from breeding birds. The call is a short, soft dju-ee. In contrast, the former subspecies have quite different songs, with sustained rattles for several seconds, or sometimes minutes. Their calls are typically sharp and monosyllabic.
Pallas's leaf warbler