The current study examined risk for young adult affective disorder in the children of parents with alcohol use disorders (AUDs), and tested whether negative experiences during the leaving home transition mediated this effect. Using multiple reporter data from a high-risk community sample, the current study included 346 emerging adults (M = 21.97 years old; 49% female, 72% non-Hispanic Caucasian, and 47% with at least one alcohol-disordered parent) from a large metropolitan area. We found that offspring of parents with AUDs were more likely to have negative experiences during the leaving home transition, which in turn predicted increased risk of affective disorders in adulthood. Parents with alcohol disorders may attempt to limit their children's independence from the family of origin or fail to appropriately scaffold their leaving home transition, which is an important developmental task, placing children of alcohol-disordered parents at greater risk of affective disorders in adulthood.