Science teacher leaders have been identified as an important lever for the implementation of science education reform. However, science reform implementation is locally controlled and not uniform across districts; therefore, the work of STLs within a reform context can vary. In this descriptive case study, we explore the work of 11 science teacher leaders who support science education reform in a variety of organizational contexts. Through the analysis of multiple data sources, we describe the roles that these science teacher leaders take up in their work and identified how variation in these roles related to localized contexts and priorities for science education. We identified seven roles that science teacher leaders enacted in their work: activist, ambassador, collaborator, innovator, networker, organizer, and translator. We found that each science teacher leader prioritized one or two of these roles in their work, with other roles supporting these primary roles. While most science teacher leaders named some aspect of collaborator, networker, and ambassador as part of their work, only the district-level science leaders named translator. Furthermore, there were important differences across the science teacher leaders in our sample, which related to their district and/or school contexts. We end with suggestions for leveraging the existing variation in the work of science teacher leaders for designing professional development including opportunities for science teacher leaders to surface the various roles they occupy in their work and to provide choice in professional learning based on those roles.