Undergraduate research and creative activities are established high-impact practices that provide students with both advanced knowledge of their academic disciplines and the ability to apply that knowledge to creatively answer questions. At the center of these experiences, is the close relationship between a student researcher and a mentor. Using survey data from 69 recent undergraduate researchers at one university, we investigated the characteristics and impact of these mentor-mentee relationships. We found that active mentoring practices were a significant influence on how competent students perceived themselves as scholars. These practices were more influential than practical aspects of mentoring. Our findings reflect the complicated nature of mentoring in higher education and identify key characteristics of successful mentoring relationships. With greater understanding of this essential component of undergraduate research, we are equipped to make more informed decisions regarding faculty and administrative support for future undergraduate research and creative activities.