This study examines the effects of using Lesson Study with pre-service secondary mathematics teachers as they moved from the methods classroom to the field experience classroom (practicum). The participants were pre-service teachers who were enrolled in a mathematics methods course in an undergraduate teacher preparation program at a private university. Lesson Study engaged the pre-service teachers in collaboratively crafting lessons, as well as field testing, revising, and re-teaching the lessons in their field placement classroom. Data were collected from weekly reflections and summative interviews of the pre-service teachers. The findings indicate that Lesson Study for pre-service teachers was an effective methodology for enhancing the efficacy of pre-service teachers due to the collaborative nature of the process, the practice teaching opportunities, and the observation of others' teaching. The pre-service teachers successfully transitioned from teaching in the methods classroom to their field experience classroom which enhanced their confidence as they entered student teaching.