University mentors require specialized knowledge and skill to support teacher candidate learning in the context of fieldwork. Without such knowledge and skill, interactions between university mentors and teacher candidates is often evaluative, thus undermining the educative potential of mentoring. We focus on mentoring practices employed in the context of the post-observation conference. Findings from a year-long implementation study show that when university mentors are introduced to an educative mentoring protocol and are provided with sustained professional development, their mentoring practices shift from an evaluative to an educative focus. University mentors indicate that this shift, initially perceived as unnatural, was supported through the scaffolding provided by the protocol and on-going professional development. Shifts in university mentors' practices supported teacher candidate reflection and growth. By foregrounding the educative function, this work adds to the theory-based conceptualization of the knowledge and skills needed for the effective mentoring of those learning to teach.