Friends of the Children employs paid and benefited professional mentors, called “Friends,” who work closely with a child as they grow to adulthood. Prior to working with children, mentors receive intensive training in areas such as effective communication skills, cultural competency, and academic support; once out in the field, they receive individual and group supervision and ongoing training. Friends of the Children conducts intensive screenings of children 4–6 years of age who are living within risky environments to identify those children at individual high risk for the development of serious problem behaviors. After identification, their parents or other primary caregivers are contacted, the program is described, and an invitation, and a commitment, is made to provide a Friend to their child until program graduation—12 plus years, after high school graduation or GED completion. If the invitation is accepted, a match is made with a same-sex Friend. Friends have small caseloads and spend a significant amount of time, week in and week out, working with and for a child. The program was founded in Portland, Oregon, in 1993 and has evolved significantly over the past three decades based not only on new inputs from the on the ground experiences of Friends, mentees, families, program administrators and other leaders, but also on new inputs from research—both from internal research at the various service delivery sites, called “chapters,” but also from external research on mentoring, child development, child psychopathology, and both the clinical and prevention sciences. In this chapter, the developmental and intervention models of the Friends of the Children professional youth mentoring program are described.