Teaching enriches students’ learning contents, while assessment evaluates students’ learning results. In recent decades, assessment has gained increased attention in EFL education. One of the important issues in the practice of assessment is the washback effect of testing on teaching and learning (Alderson and Wall, 1993; Buck, 1988; Hughes, 2003). Washback effect on teaching and learning can be positive (beneficial) or negative (harmful). Much research has been focused on the washback effect of assessment on students’ learning or large-scale, standardized tests (Watanabe, 1996). Assessment has powerful influence on teaching, too. Wall (1998) claimed that high-stakes tests might induce the impact on teaching methodology and content. This study explored the washback effect (Alderson and Wall, 1993) of a high-stakes exam, TOEFL iBT. It focused on the teachers’ perceptions of the test and its washback effect on teaching. The purpose of this qualitative study was to describe the washback behaviors of teachers and, to a lesser extent, students in the high-stakes testing environment of TOEFL iBT. The study followed a group of five teachers, teaching TOEFL iBT preparation courses. To explore the washback phenomenon, this study employed various methodological techniques, including questionnaire surveys, classroom observations, and indepth interviews.