Although the assertion that marital hostility relates to higher levels of youth adjustment difficulties has been well established, few studies have examined cooperative marital conflict in relation to youth behavior problems. This study examined the main and moderating effects of cooperative marital conflict on youth behavior problems in a sample of 416 two-parent families. Gender differences also were examined. Youth were in the sixth grade (51% females), and ranged in age from 11 to 14 (X-bar = 11.86, SD = 0.69). Cooperative marital conflict was associated with lower levels of youth internalizing problems. Cooperative marital conflict was related to daughters' but not sons' lower levels of externalizing problems. Cooperative marital conflict also served as a protective factor in the association between marital hostility and youth internalizing problems. These findings highlight the importance of examining cooperative marital conflict above and beyond marital hostility to better understand youth development during early adolescence.