Over the past two decades, the pedagogical applications of corpus linguistics to language teaching have gained increased recognition. Consequently, there has been a growing interest in developing language teachers' corpus literacy as a required knowledge base for the successful implementation of corpus-based pedagogy. Following this line of research, the current study reports on the impacts of a professional development (PD) course on six Iranian EFL teachers' corpus literacy development. Data sources for the study included semi-structured interviews, reflective journals, and classroom observations. The findings revealed that despite some barriers for using corpora in the classroom, the PD was able to expand the teachers' conceptual and pedagogical knowledge in relation to corpora and associated tools. Based on these findings, the study argues that for corpus-based pedagogy to become institutionalized, there is a need for embracing policies and practices that raise the awareness of teachers, teacher educators, and policymakers with respect to the affordances of corpora for informing language teaching.