Objective Suicide is a leading cause of adolescent death. Recent data support the efficacy of cognitive–behavioral treatments with strong family components for reducing suicide risk; however, not all youth benefit from current interventions. Identifying predictors of treatment response can inform treatment selection and optimize benefits. Method This study examines predictors of response to a DBT-informed cognitive–behavioral family treatment (SAFETY), among 50 youth with recent suicide attempts/self-harm. Youth and parents were assessed at baseline and post-treatment. Results Results indicated medium-to-large effect sizes for SAFETY on youth suicidal behavior (SB; defined as suicide attempts, aborted attempts, and planning), depression, hopelessness, social adjustment, and parental depression. Classification tree analysis, with a correct classification rate of 93.3%, and follow-up logistic analyses indicated that 35% of youths reporting active SB at baseline reported active SB at post-treatment, whereas post-treatment SB was rare among youths whose active suicidality had resolved by the baseline assessment (5%). Among youths reporting baseline SB, those endorsing sleep problems were more likely to report post-treatment SB (53%) versus those without sleep problems (0%). Conclusions These findings highlight the potential value of personalized treatment approaches based on pretreatment characteristics and the significance of baseline SB and sleep problems for predicting treatment response.