Using a case study approach, this manuscript describes the professional transformation of Gary--an Anglo, male novice teacher--by focusing on his first two years of teaching in a culturally diverse and economically disadvantaged school. As a participant of a larger hybrid, intervention project with peers, Gary received multiple hands-on and minds-on experiences for implementing sociotransformative constructivism (sTc) during the science methods courses and two summer institutes. sTc integrates cross-cultural education with social constructivism to provide a framework for teaching and learning that is more critical, inclusive, relevant, and connected to students' everyday lives. Using the structure-agency dialectic as an analytic tool, Gary's emerging sense of agency is documented in terms of two major themes: "institutional challenges and sociocultural challenges." Moving away from traditional narratives of despair, this paper offers instead a "narrative of engagement"--a frank account of the struggles beginning teachers are likely to encounter (especially in culturally diverse contexts), as well as the potential successes they could enact through their agency. Suggestions are provided for enhancing the professional preparation of science teachers and for teacher education programs and school districts to move beyond good intentions and mission statements toward more transformative action.