This study explores an EFL pre-service teacher’s self-efficacy during a teaching practicum in an Indonesian Senior High School. The researcher proposes that examining EFL pre-service teacher’s self-efficacy and her instructional judgments during a teaching practicum can reveal how self-efficacy might be favorably affected. This study used an autobiographical narrative inquiry as a method. The pre-service teacher's teaching practicum experience is examined, analyzed, and described using qualitative data from diaries. It revealed that the pre-service teacher improved her self-efficacy in teaching English. Her activities throughout the teaching practicum program contributed to enhancing her self-efficacy. From the beginning to the end of the teaching practicum, she is transitioning from a pre-service teacher with low selfefficacy to a pre-service teacher with high self-efficacy. She mentions the factors that she encountered and thought would have an impact on her efficacy over the course, including teaching observations, practicing teaching in a real classroom, interacting with the students, and getting feedback from the mentor teacher. The findings also emphasize that the school environment influenced to increase the preservice’s self-efficacy, including students’ feedback, support from other pre-service teachers, and good communication with teachers also staff members. Based on this study, implications for the EFL pre-service teacher and teacher’s education are suggested.