Teacher educators have suggested that mentoring has the potential to help novices learn to teach in reform-minded ways. This suggestion implies a change in the nature of mentor-novice relationships as conceptualized in the existing literature and an understanding of the complexities of mentoring relationships. Based on critical constructivist and social cultural perspectives of learning as well as research on learning to teach, we conceptualize 16 types of mentor-novice relationships and identify challenges and complexities associated with moving novices toward reform-minded teaching. Drawing on exemplary mentoring cases, we illustrate some of our conceptualized mentor-novice relationships and their consequences on learning to teach in reform-minded ways. Finally, we suggest that helping mentors and novices develop a shared vision for teaching and relevant beliefs about learning to teach is a central challenge for using mentoring to support reform-minded teaching.