This study investigates the effects of a TETE (Teaching English through English) class on English learners’ motivation and anxiety based on gender and English proficiency. 207 first-year high school students participated in this study and were assigned to low-, mid-, and high-level groups according to their proficiency. In the study, a background questionnaire, an English motivation questionnaire, an English anxiety questionnaire, and National United Achievement Tests were employed. The results showed that there were no significant differences between the females and the males in the four motivation components, except for the self-determination component, while significant differences were found in all motivation components among the three levels. The findings also revealed that there were significant gender differences in speaking and other types of anxiety, and they were displayed among the levels. Based on these findings, ways for English teachers to lead their TETE classes effectively and their roles in the classes are suggested. Pedagogical implications are also discussed in detail.