We use data from the Fragile Families and Child Wellbeing Study to investigate the association between co-parenting quality and nonresident fathers' involvement with children over the first five years after a nonmarital birth. We find that about one year after a nonmarital birth, 48 percent of fathers are living away from their child, rising to 56 and then 63 percent, at three and five years, respectively. Using structural equation models to estimate cross-lagged effects, we find that positive co-parenting is a strong predictor of nonresident fathers' future involvement, whereas fathers' involvement is only a weak (but significant) predictor of future co-parenting quality. The positive effect of co-parenting quality on fathers' involvement is robust across several techniques designed to address unobserved heterogeneity and across different strategies for handling missing data. We conclude that parents' ability to work together in rearing their common child across households helps keep nonresident fathers connected to their children and that programs aimed at improving parents' ability to communicate may have benefits for children irrespective of whether parents' romantic relationship remains intact.