This study investigates the development of the Reading Self-Concept and of the mechanisms underlying it, within a framework of a reading programme based on peer tutoring. The multiple methodological design adopted allowed for a quantitative approach which showed statistically significant changes in the Reading Self-Concept of those students who played the role of tutor in fixed peer tutoring. The qualitative approach of the analysis suggests that by performing the tutor's role, in an induced work atmosphere, by reading aloud and actively listening, by evaluating their effort, and engaging in meta-cognitive reflective processes, students become aware of their own capabilities and of their possibilities of improvement; thus promoting the development of the tutor's Reading Self-Concept.