Few programs to enhance fathers' engagement with children have been systematically evaluated, especially for low-income minority populations. In this study, 289 couples from primarily low-income Mexican American and European American families were randomly assigned to one of three conditions and followed for 18 months: 16-week groups for fathers, 16-week groups for couples, or a 1-time informational meeting. Compared with families in the low-dose comparison condition, intervention families showed positive effects on fathers' engagement with their children, couple relationship quality, and children's problem behaviors. Participants in couples' groups showed more consistent, longer term positive effects than those in fathers-only groups. Intervention effects were similar across family structures, income levels, and ethnicities. Implications of the results for current family policy debates are discussed.