There is a growing research interest in examining how mathematics teacher educators grow professionally in their practice. In this study, we focus on the experiences of novice mathematics teacher educators who had been secondary mathematics teachers before becoming instructors of an elementary methods course. During individual, semi-structured interviews, the participants (n = 6) described their general experience in teaching the course and shared specific incidents that informed their practice. Our analysis reveals that this specific group of mathematics educators experienced multiple layers of unfamiliarity with the methods course, including unfamiliarity related to the elementary school context and to the course students, in response to which they adopted various coping strategies. We illustrate what novice mathematics teacher educators learned from their experiences of unfamiliarity, and how their expanded personal knowledge was reflected in their subsequent teaching.