Co-parenting relationships have a significant impact on the involvement of all fathers. Fathers who report better relationships with the mother of their child report less parenting stress and more positive parenting strategies. We explore the impact of a group-based male-led and father-focused intervention on co-parenting behaviors of 385 Hispanic and non-Hispanic Black fathers. Multivariable linear mixed effects regression was used to evaluate the association of time period (pre-intervention vs. post-intervention) on co-parenting behaviors of undermining, alliance, and gatekeeping. The intervention had an impact on experiences of undermining ( p = .002), but showed no significant impact on alliance or gatekeeping. There was significant difference in all subscales by father’s ethnicity with Hispanic men reporting less undermining ( p = .001), more alliance ( p = .001), and less gatekeeping ( p = .021) than non-Hispanic Black men. Time spent with child was predictive of father’s reports of co-parenting experiences on all three subscales. Implications for group-based father-focused interventions are discussed.