This comparative case study explored the ways two elementary Teachers of Color"s science teacher identities and agency to teach science developed as they participated in a year‐long science professional development that was situated within the high‐stakes testing context of their school. The science professional development model used a dialogical approach that centered and built on the cultural backgrounds and personal experiences of the two teachers who were also coteachers in the same elementary classroom. Constructivist grounded theory and case study methods were used to analyze the three semistructured teacher interviews and four reflective teacher questionnaires collected from each teacher, as well as researcher fieldnotes. The findings showed that the Teachers of Color had different past experiences with science, and these experiences influenced the ways their social justice orientations, science teacher identities, and conceptions of science and science teaching were challenged, deepened, and broadened as they taught science and participated in the science professional development. The design of the science professional development also enabled them to enact their agency to teach science within and against school structures that marginalized science and to reposition science as a priority for themselves and their Students of Color. Implications of this study emphasize the importance of including Teachers of Color in science through professional development in ways that recognize and validate their backgrounds, knowledge, and contributions while also challenging and broadening traditional dominant discourses and school norms of science teaching, learning, and professional development.