A shift from the investigation of classroom teaching methodology, learning theoretical rationales, and areas in teacher’s linguistic/subject knowledge (Woods, 1996) into teacher cognition has emerged since the 1970s. Such a shift has a sparkle on the concern of teachers’ mental lives, i.e. the process of how they conceive (beliefs, assumptions, knowledge), implement (teaching practice), reflect on (decision-making) and reconstruct (reflection) knowledge significantly relevant to teachers’ classroom practices (Borg, 2014). The present study is a longitudinal multi-case research implemented across 1 year and 9 months focusing on what 8 Hong Kong student-teachers think, know and do during their pre-service (stage 1) and later in-service teaching practices (stage 2), and how the change of teacher cognition overtime/across context. Data collection instruments include: semi-structured interviews, classroom observations, post-lesson conferences, teaching artifacts and teachers’ own reflective journals. A narrative approach is used for data analysis and report. The present preliminary findings of stage 1 reveal that (i) teachers’ schooling defines early cognitions and shapes teachers’ perceptions of their initial teacher training (ii) professional coursework may affect existing cognitions although especially when unacknowledged (iii) contextual factors may influence practice either by modifying cognitions or else directly (Borg, 2003). Emerging from this is the understanding of “teacher cognition, schooling, professional education, and classroom practice are inter-woven” (Borg, 2014). Teacher trainers can be made aware of the significance in designing teacher education programmes and continue to contribute in longitudinal studies of teachers’ cognition as this area about teacher development across contexts from pre-service to in-service stages is still under-explored locally in Hong Kong or regionally in Asia.