As the second leading cause of death for U.S. teens, adolescent suicide is a significant public health concern. A number of recent studies show that deficits in “mentalizing,” or the ability to make generally accurate inferences about the thoughts, emotions, behaviors, and intentions of others, are linked to adolescent suicide risk. One study also demonstrated that mentalization- based treatment reduced rates of adolescent non-suicidal self-injury (NSSI). However, none of these studies used the Adult Attachment Interview (AAI), the gold standard for deriving estimates of mentalizing, and no treatment studies have examined whether improvements in adolescent mentalizing reductions in suicide risk symptoms (e.g. decreases in frequency and intensity of ideation, intent, number of attempts). The objective of the proposed study is to determine whether improvements in adolescent mentalizing predict suicide risk symptom reduction over the course of 16 weeks of psychotherapy. The study has two specific aims: 1) Determine whether adolescent mentalizing improves over the course of psychotherapy for adolescent suicide risk; and 2) Determine whether improvements in mentalizing predict and mediate improvements in suicide risk symptoms. The study will capitalize on secondary data from a recently completed RCT examining two treatments for adolescent suicide risk (Attachment Based Family Therapy and Family-Enhanced Non-Directive Supportive Therapy) (N = 129). Both treatments were similarly efficacious in reducing suicide risk symptoms. All adolescents completed pre and post-treatment AAIs, which will be coded for mentalizing. The data set includes pre- and post-treatment data (weeks 0 and 16), mid-point data (weeks 4, 8,12), and data through 1-year of follow-up (weeks 20, 32, 40, 52). This rich data set will allow for pre-post-test analyses, longitudinal growth curve modeling, and mediation analyses. Mentalizing is a core component of social understanding and synonymous with the “ability to understand mental states,” identified a key NIMH research domain sub-construct, under the broader construct of “perception and understanding of others. Accomplishing the aims of the proposed study will significantly impact knowledge about a treatment target that may be particularly important for adolescents at risk for suicide and will be a first step towards a future R01 submission aimed at: 1) building provider-friendly tools to assess mentalizing as a marker of treatment progress for youth suicide; and 2) refining youth suicide interventions to target and measure improvements in mentalizing.