This study aimed to capture the differences in the identity(s) of graduate TEFL students and teachers who did not pass any academic teacher training programs and examine the process of its construction in teaching society. Also, the impact of teacher education background on English language teachers' professional identity, agency, and beliefs in Iranian language institute teachers was investigated. For doing so, Four English teachers with less than five years of experience were compared: two had studied TEFL at university, while two had not. For data collection, Semi-structured interviews, classroom observations, and lesson narratives were used. Results showed TEFL graduates had a clearer vision of teaching and valued ongoing professional development more. They displayed greater commitment, self-efficacy, and autonomy in the classroom. Non-TEFL graduates focused on proficiency and adhered strictly to institutional policies. Regarding beliefs, TEFL graduates emphasized the value of teacher training, while non-TEFL graduates were less convinced of its necessity. Overall, a TEFL qualification positively shaped participants' professional identity and agency. However, non-TEFL graduates could still develop professionally with experience. The study highlights the importance of comprehensive teacher education in developing effective English instructors and informs decisions around staff recruitment and training.
