This study introduces a new model of practitioner research to develop an activist teacher professional identity for student-teachers and to enhance their understanding of the theory and practice of continuous professional development (CPD). The participants were ten female student-teachers enrolled in an MA program for Teaching English to Speakers of Other Languages (TESOL) at a university in Saudi Arabia. In this intervention, student-teachers constructed their version of CPD. Then they subsequently reflected on their definition of CPD and the factors contributing to its success. Qualitative research methods were used to collect data, including document analysis and individual structured interviews. The study sought to discover how the enquiry intervention improved student-teachers' grasp of CPD theory and practice and contributed to the construction of their activist teacher professional identity. The findings may encourage the development and implementation of new forms of practitioner enquiry in MA programs to support the construction of different notions of professional identity found in the literature.