In this article, the authors examine the knowledge and practice base of content-focused mentoring drawing from the wisdom of practice of a community of content mentors. The authors reveal three themes: (1) developing novices’ content teaching is a distinct and critical mentor role; (2) to support this role, experienced content mentors identified a complex knowledge/practice base, with mentors’ PCK and knowledge of assessment for content teaching as the most frequently reported domains; and (3) enactment of content-focused mentoring reveals promising practices in guiding novices in assessing and developing students’ disciplinary thinking, as well as, tensions between content-focused and socio-emotional mentor roles.