<p>As English education in Japan moves away from a native-centric English language model, many learners still feel that a native-like American accent is considered the goal to convey messages intelligibly but how necessary is a native accent? Previous studies have generally analyzed aspects of Japanese English pronunciation, including grammar, pitch, and stress, as well as opinions of Japanese speakers regarding speaking English. However, there is a lack of studies that focus on vowels and their impact on pronunciation specifically. Thus, this study aimed to combine analysis of vowels, a major indicator of accentedness, and perceptions of native speakers to create a comprehensive analysis of six key American English vowels as spoken by Japanese speakers to see the effect of Japanese-accented vowels on message conveyance in terms of intelligibility and accentedness perception. Recordings of Japanese speakers were shown to six American raters, who performed dictation tasks to judge the accuracy of the messages conveyed. The raters also used Foreign Accentedness Ratings to show their perceptions of Japanese pronunciation. Results found that although the vowels /ʌ/, /æ/, and /i/ were more likely to result in misunderstandings, even sentences spoken with accented vowels were clear enough to be deciphered by raters with an average intelligibility of 80%. This supports previous research to focus on key aspects of pronunciation rather than perfection to improve overall message conveyance in English.</p>