OBJECTIVE:To evaluate the efficacy of the Family Bereavement Program (FBP) to prevent mental health problems in parentally bereaved youths and their parents 6 years later.DESIGN:Randomized controlled trial.SETTING:Arizona State University Prevention Research Center from November 2002 to July 2005.PARTICIPANTS:Two hundred eighteen bereaved youths (89.34% of 244 enrolled in the trial 6 years earlier) and 113 spousally bereaved parents.INTERVENTIONS:The FBP includes 12 group sessions for caregivers and youths; the literature control (LC) condition includes bereavement books for youths and caregivers.MAIN OUTCOME MEASURES:Comparisons of youths in the FBP and LC on a measure of mental disorder diagnosis, 5 measures of mental health problems, and 4 measures of competent functioning; and comparisons of spousally bereaved parents on 2 measures of mental health problems.RESULTS:Youths in the FBP as compared with those in the LC had significantly lower externalizing problems as reported by caregivers and youths (adjusted mean, -0.06 vs 0.13, respectively; P = .02) and on teacher reports of externalizing problems (adjusted mean, 52.69 vs 56.27, respectively; P = .001) and internalizing problems (adjusted mean, 47.29 vs 56.27, respectively; P = .002), and they had higher self-esteem (adjusted mean, 33.93 vs 31.91, respectively; P = .005). Parents in the FBP had lower depression scores than those in the LC (adjusted mean, 5.48 vs 7.83, respectively; P = .04). A significant moderated program effect indicated that for youths with lower baseline problems, the rate of diagnosed mental disorder was lower for those in the FBP than in the LC.CONCLUSION:This study demonstrates efficacy of the FBP to reduce mental health problems of bereaved youths and their parents 6 years later.TRIAL REGISTRATION:clinicaltrials.gov Identifier: NCT01008189.