This paper reports the findings of a critical qualitative study on trauma-informed teaching of English as a second language (ESL) at Australian universities. Post-traumatic stress affects verbal learning, yet most ESL teachers do not receive training in trauma-informed teaching. The field has suffered from a dearth of empirical studies and absence of student voice. This study used a validated tool to measure the post-traumatic stress of 39 participants, including international students and former refugees. Twenty of these completed semi-structured interviews about the ESL learning environment, based on a framework of trauma-informed principles. Data were analysed using critical, qualitative methods through a trauma-informed lens. A major theme in the findings was the importance of ESL teachers' understanding of students. Within this theme, four sub-themes are explored: personal engagement and attention, acceptance and understanding of the learner role, understanding the lives of students outside the classroom and an understanding of students' cultures.