Implementing research-based practices in classrooms as a means of increasing achievement in mathematics for all students requires an understanding of many complex factors that influence classroom change. Situating the role of the teacher as critical to these efforts, teacher inquiry provides a theoretical framework from which to understand the importance of teacher-created knowledge in implementing new instructional practices. A teacher-researcher partnership may provide the support system for teacher inquiry to occur. This study investigated the effects of a research partnership on the implementation of research-based practices, specifically considering the views of teachers participating in the partnership, the differences in implementation based on interactions with researchers, and the features of the partnership that supported the implementation of new practices. Interpretative Phenomenological Analysis of secondary data was used to understand the experiences of twelve teachers who participated in a research partnership among a research-based non-profit, a national coalition of public schools, and two universities. Results from observation, survey, and interview data found teachers had a complex self-perception of their own roles in the teacher-researcher partnership including being a collaborator, a learner, and an agent of change. Additionally, teachers who interacted with researchers embraced the new materials and instructional practices more so than those who did not. Features of the partnership that were supportive of the implementation process included a focus on the teacher, evolution and responsiveness, and collaboration and integration. Implications for teachers, researchers, administrators, and others are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]