One of the most significant barriers to changing instructional practices is teachers' mindsets and beliefs about teaching and learning mathematics. This study identifies a promising new type of video club professional development that supports teachers in examining their instructional practices and mindsets. This form of professional learning is an important addition to the field due to educators and researchers are just beginning to understand more about how mindset mediates and filters belief systems that impact how instruction is implemented. The purpose of this convergent parallel mixed-methods study is to provide a deeper understanding of how the experience of engaging in video club professional development relates to teachers' mindsets, beliefs, and reflections on instructional practices. Three sources of data were analyzed: a survey, video transcripts of collaborative discussions, and written reflections. These study results extend the current video club research by including established teachers and instructional coaches. Patterns and trends emerging from this mixed method study indicate that engaging in professional development designed with repeated opportunities to (re)examine mindsets, reflect on instructional practices, and collaborate with peers causes changes in teachers' mindsets. This study adds that changes in mindsets and instruction are more likely to occur if teachers can collaboratively reconcile how new instructional strategies align with their current mathematics beliefs and mindsets. Adding a mindset component to professional development may be a promising approach to assist teachers in refining their instructional practices while examining and resetting their mindsets and beliefs. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]