Abstract This study aimed to examine the effects of a teacher education course on EFL teachers’ self-efficacy in formative assessment. The researchers employed a mixed-method design that combined quantitative and qualitative approaches to investigate the effects of the course. Thirty EFL teachers participated in the study and completed pre- and post-intervention questionnaires to assess their formative assessment self-efficacy beliefs. In addition, semi-structured interviews were conducted to gather qualitative data on teachers’ beliefs about formative assessment. The quantitative data were analyzed using paired-sample t-tests, and thematic analysis was conducted for the qualitative data. The results indicated a significant increase in teachers’ formative assessment self-efficacy beliefs. The findings suggest that providing teacher education courses focused on formative assessment can effectively enhance EFL teachers’ self-efficacy and utilization of such assessment methods in online classroom. The current study has some pedagogical implications and recommendations for the implementation of similar courses and potential areas for future research are also discussed. تفاصيل المقالة