The challenge of science achievement gaps is one that scholars have struggled to solve. Teacher leadership holds great promise in closing those gaps. Therefore, the purpose of the research reported here was to explore the responsibilities and supports of formally designated science teacher leaders (STLs) in urban elementary schools that have been successful in closing science achievement gaps. Using York-Barr and Duke's (2004) review on teacher leadership as a framework, findings from this study indicate that urban elementary STLs emphasize certain dimensions of practice (e.g., building partnerships) while deemphasizing or even omitting others (e.g., working with preservice teachers). Findings also indicate that a positive culture that supports STEM education, a principal that works with the STL yet encourages autonomy, control over scheduling, and training for the STLs seem to best support STLs. Finally, it appears that STLs would benefit from more targeted training and evaluation measures, and an STL network. Given that this study took place in schools that have been successful in closing science achievement gaps, these findings have implications for schools that wish to employ STLs to promote more equitable science achievement.