It is important to understand how teachers develop their professional identity because teacher educators and supervisors can take necessary steps to ensure novice teachers are provided necessary opportunities to cultivate their identity. This article examines research on professional identity development and explains how teachers develop their professional identity and why it is important for mentors to aid in the development process. This article draws on previous research to both define professional identity and explore the many aspects that lead to identity development in novice teachers. Findings suggest that although any experience can contribute to professional identity development, key factors have a major impact on how teachers develop their identity and the role identity development plays in pedagogical thinking. Understanding how professional identity develops can help teacher educators, supervisors, and mentors make available opportunities to build agency among novice educators, helping them to grow into reflective teachers.