This study aims to investigate English teachers’ anxiety at three different school levels in Korea with special attention to situations where anxiety is generated. A mixed method was adopted to explore English teachers’ anxiety. Quantitative data from 912 English teachers was obtained through an online survey and qualitative data was collected from focus group interviews which were conducted with three different groups of primary (n=4), middle (n=3), and high school (n=3) teachers. Quantitative data analysis showed that there were no significant differences in the level of anxiety according to three school levels, although the anxiety of English teachers gradually increases from primary to high school. On the whole, there were significant differences in anxiety according to teaching experience; teachers with less than three years of teaching experience showed the highest anxiety. Three themes emerged from the analysis of the qualitative data: fear of negative evaluation, different sources of anxiety relating to teaching experiences in the three school levels, and classroom English vs. spontaneous English. These three themes showed that English teachers’ anxiety needs to be understood in the context of anxiety-provoking situations where they are being evaluated by their colleagues about their teaching methods and English language proficiency. Pedagogical implications are discussed based on the findings of the study.