In the context of English as a global language in which the interaction is not only between native speakers and ESL speakers but also among non-native speakers themselves, there is a need to investigate how well L2 listeners can judge and successfully comprehend accented English produced by other L2 speakers; particularly, how the specific linguistic background of an L2 listener bears on their ability to understand and evaluate accented English from a speaker whose L1 is related -- or not -- to their own language. A corpus of Vietnamese accented English speech designed to elicit a careful but unguarded style of speaking was collected from 16 Vietnamese overseas students studying at an Australian University. Listeners of various L1 language backgrounds (Australian English [n= 125], Vietnamese [n=10], Chinese [n=10], Arabic [n=8], Japanese [n= 10], other=7), of varying exposure and fluency in English judged the intelligibility, the strength of foreign accent, and attempted to transcribe the test utterances in a self-paced speech recognition task. From this database it was possible to estimate (for the first time) realistic intelligibility estimates of Vietnamese accented English under conditions that approximate normal connected speech, and also to estimate the effects of the listener's language background in interaction with their comprehension proficiency in the target language (Australian English). Implications for English language teaching, particularly pronunciation pedagogy in TESOL teacher training programs are discussed.