In this article, we describe a mixed-methods study used to examine the effectiveness of a widely-used peer support program designed to facilitate the transition to adolescence and high school by enhancing self-concept and other desirable outcomes. For the quantitative component, a longitudinal design was employed (930 Grade 7 students, 3 schools, 2 years), with control group and baseline (i.e., pre-program) data against which to compare the effects. Using a multilevel approach, the results provide evidence to suggest that the program was largely successful in achieving its aims of enhancing students' school self-concept, school citizenship, sense of self and possibility, connectedness, and resourcefulness. A sub-sample of students from the experimental group participated in the qualitative component, which included open-ended survey results (n = 408 Grade 7 students, n = 75 peer support leaders) and focus groups (n = 119 Grade 7 students, n = 44 peer support leaders) to identify students' personal perspectives of the program. The qualitative results confirmed the quantitative findings that the program has important benefits for Grade 7 students and provided rich and valuable insights into students' views of the intervention. The findings of this research have important implications and suggest that the provision of peer support has the potential to a make significant contribution to schools' efforts to orchestrate positive outcomes for adolescents.