Three new species of the copepod genus Hatschekia Poche, 1902, H. lima n. sp., H. cylindrus n. sp. and H. sunaoi n. sp., are described from the gill filaments of a triggerfish, Abalistes filamentosus Matsuura & Yoshino, caught off the Ryukyu Islands, Okinawa, Japan. These new species share an unusual morphological character, i.e. four stout posterior spines on the intercoxal sclerites of legs 1 and 2. H. lima n. sp. differs from its congeners in having a robust inner lobe on the maxillule and leg 3 with a swollen basal lobe. H. cylindrus n. sp. is distinguishable from its congeners by having a cephalothorax fused to the trunk and a double-semicircular chitinous frame. H. sunaoi n. sp. is characterised by leg 3 with a swollen basal lobe and an oval cephalothorax.