English vowel productions were acoustically examined in a group of native Mandarin speakers. The first and second formant frequencies (F1 & F2) of 11 English vowels were examined in the syllable-level productions of 40 Mandarin speakers compared to 40 American English speakers. Results of the comparative acoustic analysis indicated that the Mandarin speakers differed significantly from the American English speakers in their production of several English vowels. Both male and female Mandarin speakers were also found to exhibit a compact vowel space (F1-F2) and less acoustic diversity compared to the native American English speakers. The results were discussed with regard to the impact of L1 (Mandarin) on L2 (English), the modification of articulatory pattern, and the attunement of motor skills for Mandarin speakers during L2 learning.