The present study investigated influences of Japanese and Chinese students' ability in a second language on their segmentation of English word sounds. In Study 1, Japanese students (24 monolingual students and 23 students pre-bilingual in Japanese and English) performed memory-span tasks in which the stimuli were English words with 5 different types of phonological structure. In Study 2, Chinese students (20 monolingual students and 24 students bilingual in Chinese and Japanese) performed the same tasks as in Study 1. The main results were as follows: (a) the memory span pattern in the monolingual Japanese students was consistent with the rhythm of mora in Japanese, whereas the memory span pattern in the pre-bilingual Japanese students was influenced by the rhythms of both moras and syllables; and (b) the memory span pattern in the monolingual Chinese students was not consistent with the rhythm of syllables in Chinese, whereas the memory span pattern in the bilingual Chinese students was consistent with the rhythm of mora in Japanese. These results suggest that the rhythm of mora in Japanese strongly influences the perception and segmentation of English word sounds, irrespective of whether Japanese was acquired as the first or second language.