The purpose of this study was to engage Indonesian English teachers in designing lessons for multimodal learning. Given that technological pedagogical content knowledge (TPACK) is the emerging framework that accounts for teachers’ professional expertise, this study attempts to address how to support the teachers to develop TPACK through the learning by design approach. In this study, 36 Indonesian high school English teachers participated in the teacher professional development (TPD) workshop, and 28 of them completed the pre-and-post surveys that measured teachers' perceived efficacy to apply TPACK for multimodal literacy. Paired-sample t-tests revealed that all seven factors changed significantly after the workshop, indicating the positive efficacy of TPD. Overall, our findings show that when TPD is designed with the co-design principles and relevant scaffolds, it can be effective for raising teachers’ competency in designing technology-integrated lessons and producing positive changes in teachers’ efficacy.