Persistent disconnects within and among education research, practice, and policy are limiting the reach of professional mathematics teacher communities, one of the most promising levers for humanizing mathematics teaching and learning in schools. An overarching goal of this commentary is to convince the field of mathematics education to broaden our research agendas beyond individual classrooms to teacher collectives so that our combined efforts have a greater positive impact on how people experience mathematics in and out of school. The commentary begins with a focused review of extant literature on teacher community to establish context, clarify theoretical underpinnings, and describe three important problems of teacher community. The need for research on these problems is connected to the need for studies of mathematics teacher learning to better specify what counts as evidence of learning and how this evidence gets analyzed. In response, and for the sake of epistemological and ontological transparency, teacher learning is theorized from a community-of-practice perspective. A frame analysis methodology for empirical analysis of collaborative mathematics teacher learning within professional teacher community contexts is theorized, thereby contributing provisional tools for the field to use in this work.