The research described in this study sought to understand how teacher agency was influenced by engaging teachers in action research-based professional development. Teacher agency is a critical component of teacher professionalism and nurturing teachers to recognize and enact greater agency has the potential to elevate the profession of teaching. A mixed methods methodology was employed to study the lived experience of six teachers who engaged in teacher research in a rural Alaskan school district. The research addressed this overarching question: How does engaging teachers in action research-based professional development about their professional practices influence teacher agency? In addition, data was collected to understand these supporting research questions: 1) How does participating in the action research-based professional development influence teachers' professional practices? 2) How does participating in the action research-based professional development influence collaborative practices? Findings and results suggest that the teachers' agency was influenced in the following ways: teacher engagement, knowing impact, empowerment by trust, and critical consciousness. Findings and results suggest that the teachers' professional practices were influenced in the following ways: intention and design, research capacity, determining impact, and dispositions. Findings and results suggest that the teachers' collaborative practices were influenced in the following ways: shared experience and a culture of willingness to learn. Convergence was observed between qualitative results and quantitative findings. Implications for influencing teacher agency through specific contextual conditions of professional learning and development are discussed and recommendations for the direction of future research. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]