Previous research on categorical perception of speech sounds has demonstrated a strong influence of language experience on the categorical perception of consonants and lexical tones. In order to explore the influence of language experience on vowel perception, the present study investigated the perceptual performance for Mandarin and Korean listeners along a vowel continuum, which spanned three vowel categories /a/, /ɜ/, and /u/. The results showed that both language groups exhibited categorical features in vowel perception, with a sharper categorical boundary of /ɜ/-/u/ than that of /a/-/ɜ/. Moreover, the differences found between the two groups revealed that the Korean listeners’ perception tended to be more categorical along the /a/-/ɜ/-/u/ vowel continuum than that of the Mandarin listeners. Furthermore, the Mandarin listeners tended to label stimuli more often as /a/ and less often as /u/ than the Korean counterparts. These perceptual differences between the Mandarin and Korean groups might be attributed to the different acoustic distribution in the F1×F2 vowel space of the two different native languages.