A sense of self-efficacy is an essential factor in preservice teachers' professional growth. This paper aims to explore pre-service English language teachers' sense of self-efficacy in teaching, which includes their perceptions of their teaching abilities and concerns during teaching practicum. Accordingly, this study employed a mixed methods approach with a cohort of final year students of the English language education department as the respondents. It was conducted in a university-based teacher education program in Indonesia with an online survey and interview as research instruments to collect the data. The data gathered were examined separately with descriptive statistical analysis and thematic analysis. Then, the two analyses were merged and their convergence as well as divergence were examined. This revealed that the participants' self-efficacy varied according to teaching tasks. One of their major concerns was their proficiency in the English language. The challenge related to classroom practices, including to speak fluently and accurately in the target language as well as teach it, appeared to give them pressure and affect their anxiety. Those results highlight the importance of understanding the conditions of pre-service teachers as beginning teachers, especially their teaching efficacy. Furthermore, this study strongly recommends continuous and systematic support from teachers/lecturers and school community to embrace future teachers in the teaching world.