Considering the need for writing and language programs to develop translingual and transdisciplinary pedagogies for teacher development at the graduate level (Canagarajah, 2016; Williams & Rodrigue, 2016), the authors examine the design of a multilingual pedagogy professional development series for first-year Spanish and Writing teaching assistants (TAs). As designers of and participants in the series, the authors explore the benefits and challenges inherent in transdisciplinary and translingual conversations and discuss implications for teaching and research in language and writing instruction and teacher development. In order to advance transdisciplinary and translingual approaches as a new normal in composition studies (Tardy 2017; Horner, NeCamp, and Donahue 2011), the authors hope to provide a professional development framework that adapts to the linguistic realities of different institutional contexts and students’ lived language experiences.