Previous studies have identified behavioral phenotypes that predispose genetically vulnerable youth to a later onset of bipolar I or II disorder, but few studies have examined whether early psychosocial intervention can reduce risk of syndromal conversion. In a one-year open trial, we tested a version of family-focused treatment adapted for youth at high risk for bipolar disorder (FFT-HR). A referred sample of 13 children (mean 13.4±2.69 years; 4 boys, 9 girls) who had a parent with bipolar I or II disorder participated at one of two outpatient specialty clinics. Youth met DSM-IV criteria for major depressive disorder (n=8), cyclothymic disorder (n=1), or bipolar disorder not otherwise specified (n=4), with active mood symptoms in the past month. Participants were offered FFT-HR (12 sessions in four months) with their parents, plus psychotropic medications as needed. Independent evaluators assessed depressive symptoms, hypomanic symptoms, and global functioning at baseline and then every four months for one year, with retrospective severity and impairment ratings made for each week of the follow-up interval. Families were mostly adherent to the treatment protocol (85% retention), and therapists administered the FFT-HR manual with high levels of fidelity. Youth showed significant improvements in depression, hypomania, and psychosocial functioning scores on the Adolescent Longitudinal Interval Follow-up Evaluation. They also showed significant improvements in Young Mania Rating Scale and Children's Depression Rating Scale scores. FFT-HR is a promising intervention for youth at high risk for BD. Larger-scale randomized trials that follow youth into young adulthood will be necessary to determine whether early psychosocial intervention can reduce the probability of developing bipolar I or II disorder among genetically vulnerable youth.