Without preventative intervention, youth with a history of foster care (FC) involvement have a high likelihood of developing depression and anxiety (DA) symptoms. The current study used integrative data analysis to harmonize data across four foster and kinship parent-mediated interventions (and seven randomized control trials) designed to reduce youth externalizing and other problem behaviors to determine if, and for how long, these interventions may have crossover effects on youth DA symptoms. Moderation of intervention effects by youth biological sex, developmental period, number of prior placements, and race/ethnicity was also examined. Youth (N = 1891; 59% female; ages 4 to 18 years) behaviors were assessed via the Child Behavior Checklist, Parent Daily Report, and Eyberg Child Behavior Inventory at baseline, the end of the interventions (4-6 months post baseline), and two follow-up assessments (9-12 months and 18-24 months post baseline), yielding 4830 total youth-by-time assessments. The interventions were effective at reducing DA symptoms at the end of the interventions; however, effects were only sustained for one program at the follow-up assessments. No moderation effects were found. The current study indicates that parent-mediated interventions implemented during childhood or adolescence aimed at reducing externalizing and other problem behaviors had crossover effects on youth DA symptoms at the end of the interventions. Such intervention effects were sustained 12 and 24 months later only for the most at-risk youth involved in the most intensive intervention.