Objective: Caregivers of serious juvenile offenders often hold favorable attitudes about criminality and frequently have histories of involvement in antisocial behaviors themselves. In the present study, the authors examined the long-term criminal and noncriminal outcomes for caregivers of serious juvenile offenders who had participated two decades earlier in a randomized clinical trial of multisystemic therapy (MST; Borduin et al., 1995). Method: Participants were 276 caregivers of serious juvenile offenders who were originally randomized to MST or individual therapy (IT). Criminal and civil suit data for caregivers were obtained during a 20.7-year follow-up when caregivers were on average 61.5 years old. Results: Caregivers in the MST condition had 94% fewer felonies and 70% fewer misdemeanors than did caregivers in the IT condition. In addition, caregivers in the IT condition were sentenced to 92% more days of incarceration and had 50% more family-related civil suits. Moreover, the favorable long-term effects of MST on caregiver criminality and civil suits were mediated by improved family relations during treatment. Conclusion: The present study represents the only follow-up to date of caregivers in an MST clinical trial and demonstrates the broader clinical benefits of a family-based treatment for serious juvenile offenders. Implications of the findings for policymakers and researchers are discussed.