Research on the role of teachers in supporting students with autism spectrum disorder (ASD) in schools in the Republic of Ireland has largely focused on primary and special schools rather than secondary school settings. This study examined the theoretical and practical knowledge base of Irish secondary teachers regarding the inclusion of learners with ASD using an ecological critical discursive perspective. Findings revealed teachers' strong desires to include students with ASD in their classrooms. Teachers' discourses exposed their sense of low self-efficacy in relation to pedagogical skills required to meet the needs of learners with ASD. At a school level, teachers positioned themselves outside the dominant school discourse on special education needs. Using critical discourse analysis (CDA), teachers' narratives re-focus the spotlight on issues such as ineffective legislation and inadequate policies at national level, and identified the impact that these have at a micro-analytical level on teachers' practices in relation to inclusion.