This research is a qualitative study from the perspectives of Flick Kardoff and Steinke (2004) and Nunan (1992). It is an action research study based on Kemmis and McTaggart’s theories (1988), and following the four phases provided by Burns (2010): act, plan, observe and reflect. The European Language Portfolio (ELP), developed by the Council of Europe to support the development of learner autonomy (among other objectives), was used as a pedagogical strategy to help students plan, organize, monitor and evaluate their foreign language learning process. The ELP was adapted to the context. The implementation included two important issues: a continuous process of reflection and self-assessment, and the development of five units oriented to foster the five levels of autonomy proposed by Nunan (2000) while doing language tasks. Data was collected using different empirical methods that were combined and interrelated to triangulate information. It was contrasted three voices: Students’ voice, taken from the Learning Plan, the Peer Assessment format and the Final Reflection Survey; Teacher’s voice, taken from comments on the Portfolio Hetero Evaluation grid; and Portfolio’s voice, taken from the Portfolio Hetero Evaluation grid too. Two main conclusions are drawn from data analysis: 1. When students see themselves as foreign language learners, identifying their learning styles and choosing the resources or materials that would fit them; they are able to do work more aware and engaged. 2. ELP is an accurate tool to promote autonomy since it gives students the opportunity to plan, organize, monitor and evaluate their foreign language learning processes. It let students have criteria to make decisions, set their learning goals and define learning strategies to accomplish them, it means taking charge of their own learning process. This study is a contribution to teachers who want to promote autonomy in their classroom. Using the levels of autonomy is a precise way to measure skills needed to become autonomous foreign language learners. For students the ELP strategy teaches them how to be organized and establish priorities to see a real progress in the language learning.