This research investigates non-native English teachers' engagement with the native speaker model, i.e. whether they agree/disagree with measuring English teaching and learning performance against native speaker standards. More importantly, it aims to unearth the impact of teacher education on teachers' attitudes and beliefs about "native-speakerness". Data were gathered from an online survey delivered to 85 Vietnamese TESOL teachers who had completed one of 19 Master's level TESOL programmes offered overseas and in Vietnam, followed by in-depth interviews with 20 participants. The results revealed that teacher education strengthened the teachers' beliefs about the linguistic diversity of English and led them to question the native and non-native divide by providing relevant input and opportunities to engage in critical discussion on nativeness, as well as fruitful learning experience. However, language proficiency is an area where "native-speakerness" still dominates, and where teacher education did not exert much influence. These findings shed light on the role of TESOL teacher training in influencing teacher beliefs about the native speaker model, and suggest that teacher education programmes dedicate more space for teachers to critically explore the construct of language teacher proficiency.