In this work we report on a collaborative project at a large Northeastern University, in which we explored how to best collaborate to develop interdisciplinary teaching units, which integrate intercultural citizenship (Byram, 2008) into world languages, mathematics and social studies sixth grade curricula. We argue for the importance of addressing current critical areas in education. After introducing a framework that allows teachers to focus on the development of intercultural citizenship while at the same time fostering skills in the diverse content areas, we report on how we worked with a group of graduate students, teachers and administrators in order to co-design interdisciplinary units focused on intercultural citizenship. An example of such an interdisciplinary unit is provided along with lessons learned about how we can facilitate this type of interdisciplinary collaboration. Our recommendations are based on qualitative analyses of the notes, memos and observations documented by the authors. Specifically, we share four emergent themes that illustrate how this group of educators successfully collaborated in this project: (1) Respecting disciplinary identities and boundaries, (2) Extending the understanding beyond the disciplines, (3) Ensuring a collaborative learning environment, and (4) Offering opportunities to continue the work beyond the course.