Tetraclita japonica is a common barnacle in Hong Kong, occupying a wide vertical zonation on exposed to semi-exposed shores. The length of the exopodite of cirri IV–VI of T. japonica varied with different degrees of wave exposure and tidal levels. Barnacles on exposed shores had shorter cirri than those on semi-exposed ones. Barnacles at the low intertidal also had shorter cirri than those at the high intertidal zone. Differences in desiccation and heat stress, the length of the immersion period for feeding, and predation pressure along the tidal gradient may be additional factors affecting the cirral length of T. japonica. Compared with Balanus glandula in temperate waters, the proportional difference in the cirral length of T. japonica between wave-extreme locations is much smaller (4%) than that of B. glandula (80%). Differing from B. glandula, which actively beat their cirri to feed, T. japonica exhibits prolonged extension of the cirri for feeding, which may not favour long cirri even on semi-exposed shores. Barnacles with different cirral activities, therefore, appear to have different degrees of cirral responses to environmental stimulus.