This research explored the implementation of an inquiry-based instruction integrated into the curriculum and its impact on the professional growth of the teacher educator using action research. Participants in this study were 20 pre-service teachers who attended an Educational Psychology course. The researcher collected multiple data from the participants’ responses for Student Inquiry Ability Checklist, the class learning atmosphere questionnaire, the teaching and reflection journals, and the pre-service teachers’ reports in class. The findings indicated that essential questions and questioning regarding Educational Psychology could be used to effectively create a classroom with a culture of inquiry, increase pre-service teachers’ engagement in class, and carry out self-directed inquiry learning. During the process, the researcher made good use of multiple assessments and specific feedback to raise pre-service teachers’ performance. It can be seen that the researcher and pre-service teachers constructed professional knowledge and ideas and generated connections and meanings between theory and practice. During this process, the researcher strengthened their belief in inquiry-based instruction from reflection, reduced the conflict between teaching pressure and student learning outcome and constructed a transforming model of inquiry-based instruction. Suggestions for implementing a similar curriculum were proposed for future studies.