American English vowels are challenging for non-native speakers of English, because the vowels’ articulation is generally difficult to observe and describe. Although a computer has been applied for language learning, human instructors are still preferred because of pedagogical flexibility and personal interaction. This preliminary study compared two short-term methods: computer feedback only (Group I) and computer feedback with instructor’s assistance (Group II), on American English vowel production for Japanese adults. Recordings of Japanese vowel productions of pre- and post-trainings in two groups were evaluated by three native speakers of English. Overall the results demonstrated a slight improvement of the vowel productions for Group II, however, no change was found for Group I.