I focus my research agenda on mathematics teachers’ learning opportunities in three contexts: the preservice level, the teacher educator level, and the inservice level. It is a line of inquiry strongly called for in the field of mathematics education, and most recently articulated in the field’s premiere journal, Journal for Research in Mathematics Education (JRME): “How can we improve the impact of research on practice?” The JRME editors argue that we must challenge the current divide between research and practice and adopt a system that emphasizes “learning opportunities as an integral element of research that has an impact on practice” (Cai et al., 2017, p. 466, italics added). My research agenda aims to contribute scholarly products related to the learning opportunities and factors that influence mathematics teachers’ learning (their students’ math learning) and their pedagogical content knowledge (PCK) development within interconnected lines of inquiry at three levels: a) preservice level, including learning opportunities that improve prospective elementary and middle school teachers’ readiness to teach mathematics in responsive and responsible ways; b) teacher educator level, examining the teaching practices of mathematics teacher educators who teach prospective elementary and middle school teachers; and c) inservice level, including learning opportunities and factors that influence inservice teachers’ learning, as well as their motivation to learn and engagement in professional development.