Teachers' professional identities are continuously being shaped by new knowledge gained through continued coursework and professional development (PD). Traditionally, PD programs and coursework tend to focus on assets such as knowledge or competencies but forego helping students answer questions about their professional identity. This study examines the professional identity development of content-area teachers earning an English as a Second Language endorsement in an online PD program. Using thematic analysis to analyze reflective writings, the researchers examine the identity development of these teachers. Even with the short duration of the PD, changes in professional identity occurred. Shifts included participants' views on appropriate methods and instructional strategies in the ELL classrooms, their contextual understanding to support ELLs based on their teaching experience and pedagogical approaches, and their overall perception about the social constructs ELLs are experiencing. The change allowed the participants to increase their effectiveness in working with ELLs.