The purpose of this study is to explore how a university-school partnership in Canada supports pre-service teachers in developing positive perceptions about learning and teaching Science, Technology, Engineering, and Mathematics (STEM) in their teacher preparation programs. This initiative provided opportunities for pre-service teachers to understand STEM as a boundary-object (i.e. S.T.E.M) and work in communities of practice toward creating and implementing lesson plans with K-12 students. Using a non-random pre- and post-intervention research design, we examine the effectiveness of this initiative by analyzing survey responses from 43 pre-service teachers. The survey consisted of 37 Likert-scale responses measuring agreement on statements relating to pre-service teachers' feelings about learning and teaching S.T.E.M. The initiative had a positive effect on pre-service teachers' perceptions and feeling of competence in teaching mathematics and S.T.E.M as a whole, their perceptions of learning S.T.E.M, and views on teaching S.T.E.M. Also, findings revealed some differences in responses by age, undergraduate field of study, and program stream. We discuss these findings and their implications for pre-service teaching programs, emphasizing S.T.E.M as a boundary-object and building communities of practice as 2 primary factors.