Abstarct: Abstract Despite the rising interest in studying teacher career development, a literature review indicated that an important variable has been left out of this research: teacher wisdom as a cognitive component that Bandura (1978) states is central to teacher efficacy formulation. Accordingly, there is an urgent need to understand how teachers become experts and what has been changed in their perspective, beliefs, and practice during their years of experience from their point of view. This research aims to understand teachers’ perceptions of how teaching experience has changed their knowledge and practice and what they have learned from their teaching experience. To this end, 8 Iranian EFL teachers were selected through a purposeful sampling method, all with sufficient experience teaching English as a Foreign Language in different schools in Iran. Moreover, following a Constructivist Grounded Theory of Charmaz (2006), data was collected through in-depth interviews and then analyzed respectively. The research findings were clustered under two major classifications: a) change in practice and 2) change in cognition. This research’s findings have implications for those who work in the field of Language teaching, teacher career development, and EFL teacher educators.