With the shift in the field of teacher education, where english language teaching presents a much higher level of professionalism than before (richards, 2008), teacher education institutions have been emphasizing the importance of encouraging student-teachers to pursue alternatives for the problems they may find in their classroom context. johnson (2009) argues that second language teacher education should provide teachers the tools to help them to construe their instructional experiences grounded on theory about language learning and teaching. thus, drawing on sociocultural theory (vygotsky, 1987), which emphasizes that learning and development are situated dynamic processes which occur through social relations, the present study aims at investigating to what extent the use of the european portfolio for student teachers of languages (epostl) in combination with class activities contribute towards teacher professional development. this qualitative research was conducted as a microgenetic study, and the participants were six student-teachers from letras – english licenciatura undergraduate program at a federal university in the south of brazil. they were accompanied along four months while doing an elective course in teaching practice, in which they were asked to keep a portfolio where they should record information regarding their development. all their interactions with teacher educators and peers during the lessons were video recorded and all class materials were gathered in order to compare their narratives in the portfolio to their actual development, especially during their microteaching presentations and feedback sessions. results indicate that the student-teachers had the opportunity to reflect on their learning experience during this course, as they made use of the epostl and class activities to describe and to make sense of some new concepts they were exposed to during their classes. their narratives funcitoned as mediational tools in order to regulate own thinking and internalize these concepts, as well as reinforced the notion that concept development indeed follows a twisting path (vygotsky, 1986). the portfolio helped the student-teachers to make their learning process explicit by exposing their understandings and served as a resource where they could recognize their strengths and their weaknesses. the epostl and the class activities also helped student-teachers to relate their experiences to theoretical principles in order to reduce the gap between theoretical knowledge and teaching practice and allowed them to systematically anchor their instruction to a set of principled statements by merging scientific concepts with situated understandings and practices.