Through a qualitative analysis of data collected over four years of design-based research on the implementation of a reform-oriented mathematics curriculum, this study describes two sixth-grade teachers’ changing views of the role and place of reading in mathematics instruction. The findings reveal the evolution of the teachers’ perspective on mathematics instruction from one that did not include reading toward one in which reading was viewed as integral to students’ mathematics learning. The teachers’ views on reading in mathematics at the end of the project lend empirical support to theoretical propositions for a disciplinary literacy approach to mathematics instruction. At the same time, their views nuance such propositions by highlighting differences between the reading demands of school mathematics texts and those of disciplinary texts.