The aim of this paper is to share part of an ongoing study in which we are interested in introducing a Gallery Walk (GW) as an instructional strategy to contemplate in the classroom, in the context of preservice teacher training for elementary education (6-12 years old), to promote students' mathematical knowledge and skills, through problem solving abilities. In this study we intend, in particular, to identify the strategies used by students when solving challenging tasks with multiple approaches, using a GW, as well as characterize their reaction during their engagement in the GW as a teaching and learning strategy. A qualitative and interpretive study, with an exploratory approach, was adopted and the collected data included classroom observations and written productions. The results allowed to identify the strategies used by the participants and to verify the potential of the GW in the quality of the written productions and discussions, which proved to be more effective than in more traditional discussions, allowing to increase the repertoire of solving strategies of each student and communication and collaborative skills; it had a positive effect on the participants' achievements and it was an enjoyable and rewarding experience for all of them.