Socioscientific Issues (SSI) provide a strong framework for engaging students and teachers in meaningful and relevant scientific discourse in the development of functional scientific literacy. However, while most teachers recognize the value of introducing students to SSI, they themselves have limited knowledge of SSI and often lack the confidence and support to teach these issues. For this study, the SSI framework provided a lens for exploring and understanding how 24 pre-service and in-service teachers navigated science, technology, engineering, and mathematics (STEM) curriculum to incorporate SSI into their classroom practice. The following questions guided our inquiry: (a) In what ways, if any, do practicing elementary classroom teachers' notions of SSI, with particular attention to reducing carbon dioxide, change before and after completion of a STEM and Society course? (b) To what extent do practicing elementary teachers change their implementation of SSI in their lessons and classroom instruction? The findings of this study showed positive views of teaching controversial and complex case-based issues. The reasons our teachers provided included raising environmental awareness, teaching social responsibility, and teachers' interest on SSI topics. Our findings also supported development of the cultural issues component of SSI that we can attribute to teachers' field experiences in Pennsylvania, USA and in Sicily, Italy, which included shifts on teachers' perceived cultural practices, reducing carbon dioxide, and teaching of SSI in their classrooms. Our study can potentially provide useful resources for developing STEM education programs and courses with research-based content and methods for introducing new contexts to elementary science teachers.