High U.S. incarceration rates have motivated recent research on the negative effects of imprisonment on later employment, earnings, and family relationships. Because most men in jail and prison are fathers, a large number of children may be placed at considerable risk by policies of incarceration. This article examines one dimension of the economic risk faced by children of incarcerated fathers: the reduction in the financial support that they receive. We use a population-based sample of urban children to examine the effects of incarceration on this support. Both cross-sectional and longitudinal regressions indicate that formerly incarcerated men are less likely to contribute to their families, and those who do contribute provide significantly less. The negative effects of incarceration on fathers' financial support are due not only to the low earnings of formerly incarcerated men but also to their increased likelihood to live apart from their children. Men contribute far less through child support (formal or informal) than they do when they share their earnings within their household, suggesting that the destabilizing effects of incarceration on family relationships place children at significant economic disadvantage.