The authors captured and ringed a willow warbler at Mt. Takachiyama (28°09′51″N, 129°19′08″E) in Setouchi Town, Kagoshima Prefecture, southern Japan, on September 27, 2001. The bird was identified as this species from following morphological and genetic characteristics. Morphologically, the bird had no wing-bars and long tail (tail/wing ratio: 0.75), 6th primary (P6) was not emarginated, the outermost primary (P1) was longer than primary-coverts by 5.6 mm, and wing-point was 3rd primary (P3). Blood sample was taken with a micro-capillary tube from ulnar vein before releasing and was preserved in Queen's buffer (Seutin et al. 1991) at the ambient temperature. A part of cytochrome b sequence was determined using an automated DNA sequencer (Model 310, Applied Biosystems) following Leisler et al. (1997). The captured bird (GenBank Accession #: AB075024) differed from a European willow warbler (Accession#: Z73492) by 9 substitutions (1.5% sequence divergence), which is typical of a subspecies distance. The bird was probably race yakutensis judging from the distribution, but it could not be confirmed.