National shortages of math and science teachers have led to a variety of strategies and programs to attract second career professionals into teaching. This qualitative study explores the development of professional teaching identities in six STEM career changers in a post-baccalaureate pre-service teacher credential program in California. Findings suggest the career changers relied upon skills developed in their previous careers to navigate through a new profession; however, returning to the life of a student again was difficult. Additionally, the career changers in this study valued interacting with their traditional aged peers in the program as these relationships were beneficial to their own socialization into teaching as they developed their teacher identities.