Intellectual humility is an intellectual virtue where humility and the pursuit of epistemic goods intersect. As of this dissertation being written, intellectual humility had been studied in psychology and philosophy, but not from the perspective of the teacher in 6th-12th grade mathematics. Hence, this Grounded Theory study sought to develop a theory for intellectual humility while teaching 6th-12th mathematics. This study was guided by research questions focused on beliefs teachers held while practicing and characteristics of intellectual humility while teaching. These questions helped answer the main research question: What is intellectual humility for teaching 6th-12th mathematics? Three participants helped form this theory, and triangulation of interviews, observations, and artifacts were used to maintain ethical and virtuous data collection and analysis. Findings indicated teachers believed their students to be viable contributors to mathematics conversations, allowing them to treat students as future equals. As such, teachers learned from and with students during interactions via productive mathematical discourse. Therefore, intellectual humility was revealed in the interactions with students as teachers listened to learn from and with students. Teachers displayed characteristics of existing virtue theories as well, such as admitting their knowledge to be incomplete, appreciating the intellect of others (students), and balancing being a member of the learning community with being an expert in the subject. This research gives credibility to the importance of incorporating intellectual humility for practicing teachers, administrators, and mathematics teacher educators. [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.]