This sequential mixed methods study applies a recently published model of integrated science, technology, engineering, and mathematics (STEM) teacher identity to analyze teacher artifacts from a graduate STEM education course for in-service teachers (n = 23). This model captures the complexity of integrating STEM in elementary classrooms as an intertwining of professional teacher identity and STEM learning identity. Increases in participating teachers' self-efficacy and STEM career awareness motivated the research team to look for explanatory qualitative evidence in teacher reflections. Analysis using the nine dimensions of the model elicited robust evidence of professional teacher identity (teaching interest, self-efficacy, motivation, self-image, and task perception) and limited evidence of STEM learner identity (competence, performance, recognition, and content interest) in teachers' identity statements. Changes in self-efficacy and STEM career awareness were associated with only three of nine identity dimensions. Application of this model of integrated STEM teacher identity can provide a deeper understanding of teacher readiness to engage elementary students in authentic problem solving. Findings indicate that purposeful prompting of reflection in STEM teacher education informed by the model may support the cultivation of integrated STEM teacher identities.