Science, technology, engineering, and mathematics (STEM) teacher advocacy is a particular skillset within STEM teacher leadership, but little is known about how STEM teacher leaders develop their identity as advocates for STEM education. To glean a more nuanced and deeper understanding of developing advocate identity among STEM teacher leaders, we conducted a duoethnographic study to critically reflect on our lived experiences as STEM teacher leaders engaged in advocacy. Drawing upon identity theory to frame our study, we co-developed and individually responded to a set of questions and prompts that critically interrogated our experiences, leading toward identifying as advocates for STEM education. Multiple subsequent critical discussions about our responses led to a recorded dialogic conversation, which acted as our site of research. Emergent themes from duoethnographic analysis revealed having increased awareness of STEM education policies and their impacts, recognizing injustices affecting marginalized communities, and acknowledging systemic barriers preventing community voices in policymaking helped to strengthen our advocacy identities. The dialogue also emphasized the importance of reaching out to communities to understand needs when developing policy recommendations. We conclude the study by making recommendations to support STEM teacher leaders interested in engaging in advocacy at the individual classroom, school, and district levels.