Transnational teacher educators, who cross national, social, and cultural boundaries to prepare teachers, play a vital role in nurturing teachers' awareness and appreciation of learner diversity. However, transnational teacher educators tend to encounter tremendous challenges in developing their professional identities. To date, though many studies have investigated how teachers and teacher educators in general develop their professional identities, scant attention has been paid to that complex process of "transnational" teacher educators. To begin to close this research gap, this collaborative autoethnographic study examines how we develop our teacher educator identities through teaching a diversity course in the United States as transnational teacher educators from China and South Korea. The findings reveal that our transnational backgrounds (e.g., speaking English as a second language and holding particular cultural beliefs) initially challenged our identity development, but our continuous teaching and learning within a supportive institutional context turned the marginality of our transnational backgrounds into professional assets. The research findings can extend our understanding of teacher educators' identity development. The study also suggests practical implications for teacher education programs to create an inclusive and supportive professional community in which all teacher educators may grow.