Breeds central, southern and eastern China (southern Gansu and Sichuan east to Hubei and Fujian, south to Guizhou, northern Guangxi and eastern Guangdong), also central Laos and northern Vietnam (central Annam). Non-breeding also northern and eastern Thailand, southern Laos and northern Vietnam (western and eastern Tonkin, northern Annam).
 
Population
Estimated population is unknown (2010).
Sulphur-breasted Warbler (Phylloscopus ricketti) [XC240665]
by Jim Holmes from (Phnom Aoral) \u1783\u17bb\u17c6 \u178f\u17d2\u179a\u1796\u17b6\u17c6\u1784\u1787\u17c4, \u179f\u17d2\u179a\u17bb\u1780\u17b1\u179a\u17c9\u17b6\u179b\u17cb, \u1781\u17c1\u178f\u17d2\u178f\u1780\u17c6\u1796\u1784\u17cb\u179f\u17d2\u1796\u17ba, Cambodia (song)
Sulphur-breasted Warbler (Phylloscopus ricketti) [XC631763]
by Bram Piot from Nam Kat Yorla Pa (waterfall road), Oudomxay, Laos (song)
Subspecies
No subspecies.
Has sometimes been treated as conspecific with Yellow-vented Warbler (Phylloscopus cantator). Subspecies goodsoni of Blyth's Leaf-Warbler (Phylloscopus reguloides) was formerly placed with this species.