Despite the increasing practice and evidence of its potential, co-teaching has not become a widespread practice in schools yet. Research shows the need of helping teachers become aware of co-teaching as a good mechanism for peer learning among teachers. This study focuses on the changes in student teachers' attitudes to use co-teaching through their perceptions as a tool for their own learning. Opting for a mixed-methods sequential explanatory design, 82 student teachers were divided into two groups, one receiving only conceptual training and the other one having the possibility to experience co-teaching in schools. It was hypothesized that the second group would improve their attitudes to use co-teaching more than the first group. A qualitative study was carried out to explore (1) students' learning perceptions, (2) learning episodes in the out-of-class joint activity and (3) comparison between (1) and (2). Results confirm the hypothesis and find evidence from learning episodes to support students' perceptions but show that there is not a clear match between students' perceptions and contents from the learning episodes. Research implications and limitations are discussed.