This article presents the results of a study conducted to identify the perceptions of bilingual and ESL pre-service teachers regarding the integration of a collaborative service learning project in a key course of their teacher preparation program. Pre-, process, and final reflective essays were written by participants as they engaged in the development of an ESL unit to teach language through content to ELLs. The analysis of participants' reflections revealed that preservice teachers connect the learning they acquire in their teacher education program with their life experiences, which contributes to their identity formation as prospective teachers of ELLs. In addition, participants discovered the value of collaboration in their professional development as they applied and articulated effective practices in the instruction of ELLs. The integration of meaningful collaborative projects and reflective exercises in teacher education programs is suggested.