The species is native to Japan, where it has been designated a Natural Monument under the 1950 Law for the Protection of Cultural Properties,[6] with records also from Taiwan and the Philippines.

[1] Ijima's leaf warbler is a monotypic species first described by Leonhard Stejneger in 1892, based on three specimens collected in the spring of 1887 by Namie Motokichi [ja] on Miyake-jima and Nii-jima, in the Izu Islands of Tokyo.

[2] Initially given the scientific name Acanthopneuste ijimae by Stejneger,[7] Momiyama Tokutarō [fi] followed suit in a 1923 paper on the birds of Izu Ōshima.

[15][18] Insects form the principal component of its diet — when written in kanji (飯島虫喰),[17] the warbler's Japanese name reads as "Ijima's insect-eater" — which also includes seeds.

[18] For these it forages, singly or in small groups (sometimes including other species, in particular long-tailed tits (Aegithalos caudatus)), on lower branches, in the forest canopy, and on the ground, and it may also take prey in mid-air.

[18] With an estimated 3% of the global population, Phylloscopus ijimae (Chinese: 飯島柳鶯) is included on the 2016 Red List of Birds of Taiwan with the status "vulnerable".