Centering on cognitive and reflective development of pre-service primary school teachers, this study aimed to contribute new understanding of how teacher identity is formed through increased teacher self-efficacy by preservice teachers trained in cognitive coaching developed by the researcher. Its purpose was three-fold: examining the impact of cognitive coaching on: (1) development of student teachers' reflective practice in planning and conducting a lesson, (2) teacher sense of efficacy, and (3) identity formation. A cognitive coaching program, for which 26 student teachers were trained, was mainly prepared to focus on cognitive coaching. Obviously, treatment had a significant impact on both teacher sense of efficacy and formation of professional identity. Findings suggest new principles and practical implications for teacher trainers on how cognitive coaching could be implemented both in teacher training and school-based contexts to seek the paths to increase teacher sense of efficacy and help shape teacher identity.