The present study aims to examine the realization of English reduced vowels by Korean learners. Little seems to be known about the acquisition of reduced vowels by L2 learners in spite of the importance of their correct use in avoiding a foreign accent. Three groups of Korean subjects and native American-English subjects participated in the study, and five types of test materials were created considering phonological position, morphological structure, and English orthography. The frequencies of F1 and F2 were measured and their scatter plots were drawn for the analysis. The findings of the present study are summarized as follows. First, L1 influence was identified in the realization of English reduced vowels by Korean learners. The characteristic of the syllable-timed language of Korean was represented and L1 transfer of the Korean vowel [ ] was shown in the results. Second, English proficiency of Korean learners was reflected in the production of the reduced vowels. Third, the early experience of staying in English-speaking countries helped Korean learners acquire English reduced vowels.