The integration of technology into science teaching by pre-service science teachers and their self-efficacy in using technology in their teaching practices are important issues for science education. The purpose of this study is to develop an Educational Robotics Technological Pedagogical Content Knowledge (ER-TPACK) self-efficacy scale based on a transformative TPACK framework. The data obtained from 266 pre-service science teachers were divided into two groups as 133 participants for generating exploratory factor analysis (EFA) and 133 participants for generating confirmatory factor analysis. Results of the EFA indicated that the ER-TPACK self-efficacy scale including 33 items loaded on a single factor. Cronbach's alpha coefficient for sample 1 and sample 2 was 0.98. The findings revealed that the scale was a valid and reliable instrument for measuring pre-service science teachers' ER-TPACK self-efficacy.