Objective: This study examined the effects of Parent Management Training, Oregon (PMTO) model on parenting effectiveness and caregiver functioning. Method: Children in foster care with emotional and behavioral problems were randomized to PMTO (n = 461) or services as usual (n = 457) in a nonblinded study design. Using an intent-to-treat approach, analysis of covariance models tested the intervention's overall effect and time interactions for parenting and caregiver functioning. Additional analyses were conducted to identify significant predictors of outcomes. Results: PMTO did not significantly affect parenting practices; however, positive effects were observed on caregiver functioning in mental health (odds ratio [OR] = 2.01), substance use (OR = 1.67), social supports (OR = 2.37), and readiness for reunification (OR = 1.64). While no time interactions were detected, several child, parent, and case characteristics were associated with improvements in 6-month outcomes. Conclusion: This study extends evidence on PMTO to biological families of children in foster care, including those with older youth.