This study investigated the continuous influence of self-assessment on EFL (English as a foreign language) learners' self-efficacy. The participants, divided into an experimental and a control group, were 57 Iranian EFL learners in an English-language institute. The participants' self-efficacy was measured through a questionnaire that was the same for both groups. Additionally, the participants in the experimental group completed a biweekly self-assessment questionnaire throughout the semester. The obtained data were analyzed through an Analysis of Covariance (ANCOVA). The findings showed that the students' self-efficacy improved significantly in the experimental group. This suggests that applying self-assessment on a formative basis in an EFL setting leads to increased self-efficacy. This study thus highlights the pedagogical implications of self-assessment in EFL classrooms.