As social-justice mathematics teacher educators, we have always engaged and supported the prospective and practicing teachers in our classes in critical reflection about mathematics and the teaching and learning of mathematics (Felton, 2010, 2012; Felton & Koestler, 2012; Koestler, 2012). Although there are different notions, purposes, and traditions of reflection (Zeichner & Liston, 1996), critical reflection goes beyond teachers simply recounting their experiences and instead engages them in attempting to unpack and make sense of their experiences in terms of the social, political, and cultural contexts in which their work takes place. We believe this can support them in taking up more progressive pedagogies that can lead to more equitable and just mathematics education for all students. While we did not originally think about our work in terms of teacher agency, writing about this here and elsewhere (Felton & Koestler, 2012) has provided an opportunity to consider what role agency plays in our work, what agency in mathematics teacher education means to us, and how we may better support developing this form of agency in our future work as mathematics teacher educators. We have been collaborating as "critical friends" (Anderson, Herr, & Nihlen, 2007) for the past eight years by discussing the content and pedagogy of our courses, our theoretical frames, and our research methods. While, in this article we discuss data that were generated in one semester of a mathematics content course for prospective teachers taught by Felton, analyzing and theorizing about the data was a collaborative effort.