The genus name Phylloscopus is from Ancient Greek phullon, "leaf", and skopos, "seeker" (from skopeo, "to watch").

[6] Western Bonelli's warbler is a small passerine bird, found in forest and woodland.

[7] Cuckoo nest predation and brood parasitism are major hazards to the breeding success of western Bonelli's warblers.

The adult has a plain grey-green back, green-toned rump and wings and whitish underparts.

The song is a fast monotone trill, only slightly different from eastern Bonelli's, and also with some similarity to the wood warbler.