Currently, STEM education and Education for Sustainability (EfS) are viewed as disconnected educational approaches in Pennsylvania classrooms. While both offer promising outcomes and have overlapping goals, research shows that separately they both face challenges to implementation. This study aims to strengthen both approaches by exploring the extent to which STEM educators use sustainability contexts in their classrooms. Additionally, it investigates whether educators' competence in systems thinking, a skill emphasized in both areas, influences this integration. Using a scoping literature review and mixed methods approach, the study found that STEM educators often have simplified, incomplete perspectives of sustainability, with educators of higher grades showing significantly greater comprehension than lower-grade counterparts. A positive correlation between educators' systems thinking competency and their recognition of the importance of EfS in STEM education was identified, highlighting an interconnection between these domains. This study revealed barriers beyond sustainability knowledge hinder its integration into STEM lessons. These findings offer suggestions for various levels of stakeholders across Pennsylvania, including tailored professional learning for different grade levels and an emphasis on developing educators' systems thinking competence. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]