A Booted Warbler Hippolais caligata was observed on Hegura Island, Ishikawa Prefecture, from 26th to 29th of September in 1999, two days after typhoon No. 18 of that year passed the northern sea area of the island. The bird was rather pale grayish-brown above and buffish white below, it had a high crown with a flattish forehead which appeared slightly rounded, a prominent brownish-white supercilium extended behind the eye with faint dark bordering along the upper edge (narrow in front of the eye and markedly broad at rear), a faint dark eye-stripe, a short and slender bill (shorter and finer than that of the Arctic Warbler Phylloscopus borealis) formed by dark upper mandible and a pale lower mandible with a dark tip. The greater coverts comprised dark-centred feathers with pale fringes, with the remiges occasionally forming wing-panel in the secondaries, there was a short primary projection about half the length of the longest tertial, a grayish-brown square tail with pale edges of outer feathers, shorter undertail-coverts and a pale pinkish grey tarsus. The bird was active and often moving through undergrowth, but sometimes fed on the ground, hawked and perched on wire. The bird rarely vocalized, except once when it uttered a ‘chat’ in a low voice. This bird had features of four Hippolais spp. which have short and fine bills; the Booted H. caligata, Syke's H. rama, Eastern Olivaceous H. pallida and Western Olivaceous H. opaca Warblers. It was identified as a Booted Warbler because of 1) its rather round head, 2) obvious supercilium extending behind the eye with a faint dark bordering upper edge, 3) the contrast between dark centers and pale fringes in tertials, 4) the short bill with a dark-tipped lower mandible, and 5) its high activity. This is believed to be the first record of the Booted Warbler in Japan.