Purpose: An increasing number of schools and districts across the US are requiring teachers to collaborate for the purpose of data-driven decision making. Research suggests that both data use and teacher collaboration are important ingredients in the school improvement process. Existing studies also reveal the complexities of teacher collaboration and the importance of context in shaping teachers' collaborative work, especially with data. Yet, the intersection of teacher collaboration and data use has been understudied. The purpose of this paper is to examine the affordances and constraints that exist in the context of established teacher collaboration time for the purposes of data-driven decision making. Design/methodology/approach: The paper draws upon qualitative case study data gathered in six schools that structured teacher time for collaboration on data use. Findings: An analysis of the data revealed that a variety of leadership activities and organizational conditions shaped teachers' collaborative work with data. These included leadership focused on thoughtful use of data and the framing of data-driven decision making in terms of collective responsibility; the establishment of norms for teacher collaboration; the implementation of data discussion protocols; and teacher groupings and subject matter subcultures. Originality/value: Knowing how and when a leadership activity or organizational condition becomes either an affordance or a constraint to teacher collaboration around data use has important implications for leadership and educational change. The findings of this study also help to lay the groundwork for future research regarding teacher collaboration around data use. (Contains 1 table.)