How do the personal epistemological beliefs of instruction librarians inform their teaching practices? By learning about their personal beliefs about knowledge acquisition, are librarians better equipped to create an environment more conducive to student learning? These questions informed a mixed-methods research study. Using the Approaches to Teaching Inventory, 283 teaching librarians answered 22 questions about their teaching practices and how they believe students learn. We interviewed 12 of these librarians to learn more about their teaching practices and epistemological beliefs. Seven themes emerged as influences on the instructional practices of librarians that ranged from learning biases to classroom tensions.