Developing teachers’ professional agency through standard models of instructional designs is critical in helping them deal with the barriers in designing and implementing online learning environments. Therefore, the purpose of this study was to explore the role of an ADDIE (Analysis–Design–Development–Implementation–Evaluation) model of the computer-assisted language learning (CALL) teacher preparation program (TPP) in developing TEFL (teaching English as a foreign language) student-teachers’ professional agency (PA). We conducted an instrumental (exploratory) case study to explore the PA development of 18 TEFL student-teachers who took a CALL course that was designed based on ADDIE. The deductive thematic analysis of student-teachers’ autobiographical narratives, unstructured interviews, and course projects showed that each stage of ADDIE contributed to developing the dimensions of the PA. We concluded that the constructive role of the ADDIE model of CALL TPP in developing TEFL student-teachers’ PA might be due to ADDIE’s capability to construct a context for developing student-teachers’ dynamic capacity to tackle educational concerns and provide a context of playing different professional roles. The study bears implications for TEFL teacher educators to consider the action-based nature of PA when the ADDIE model is implemented.