Collaborations between mathematicians and mathematics teacher educators are increasingly being expected, and realized, within the context of mathematics teacher education. Most research related to collaborative efforts between members of the mathematics and mathematics education communities has focused on the products, rather than the process of collaboration. In this article, I present the results of an interpretative phenomenological analysis investigating the lived experiences of a mathematician and a mathematics teacher educator as they team-taught a mathematics content and mathematics methods course for prospective secondary mathematics teachers. I present extracts from interviews to illustrate the instructors' perceptions that through collaboration and participation in the practice of the "other," they were able to increase the awareness of their own practice and the practices characterizing their respective communities. The results of this study illustrate the potential of collaboration across these communities as a form of professional development for mathematics and mathematics education faculty.