The research reported in this paper focuses on New Zealand secondary mainstream teachers’ awareness of their role in the teaching of English Language Learners (ELLs). Recent Ministry of Education publications regarding the teaching of ELLs have made it clear that mainstream subject teachers are expected to play an increasingly important role in facilitating English language acquisition, rather than this being the sole or main concern of ESOL specialist teachers. For example, the English Language Learning Progressions (ELLP) (2008) states that the publication has been designed to “explain what ESOL specialists and mainstream teachers need to know about English language learners in order to maximise their learning and participation”. The implication of this is that mainstream teachers are now expected to become informed about effective teaching of ELLs. The main aim of the research was to obtain an overall picture of the extent to which mainstream teachers are aware of their role in teaching ELLs. A secondary aim was to ascertain to what extent mainstream teachers are using the materials and resources that are currently available to support their teaching of ELLs. In the research, secondary mainstream teachers were asked to complete a questionnaire about their knowledge of various aspects of teaching ELLs and the importance of having this knowledge. Questions focussed on teacher knowledge of learners’ backgrounds and level of English, and teacher knowledge of and use of strategies for teaching ELLs. Teachers were also asked to identify factors that had either assisted or hindered them from learning more about their ELLs or strategies for teaching ELLs. The research has applications for secondary mainstream teachers in general, and for those who train or provide professional development for secondary mainstream teachers.