The current study examined low‐income, unmarried, nonresidential fathers’ engagement in co‐parenting with the child's mother. Qualitative interviews were conducted with 71 fathers attending nine different fatherhood programs in five cities that serve low‐income, primarily unmarried, nonresidential fathers. The results revealed that co‐parenting in this sample of fathers is a multidimensional construct that includes both negative and positive components. Our results also point to specific behaviors or indicators that seem to be unique to this population of fathers and mothers and that should be used to inform the development of measures of co‐parenting. The need for such measurement development is important given the growing number of unmarried, nonresident fathers and the resources that are currently being invested by federal, state, and local governments to improve low‐income, unmarried, nonresidential fathers’ involvement with their children. Key Points for the Family Court Community Co‐parenting relationships among low‐income, unmarried, nonresidential fathers and mothers are multidimensional and include both negative and positive components, including undermining, gatekeeping, parenting alliance, conflict, support, and division of labor. The components of co‐parenting that are relevant to co‐residential fathers and mothers are also relevant to low‐income, unmarried, nonresidential parents. Co‐parenting relationships between unmarried, nonresidential mothers and fathers often times involve another adult, particularly the father's new partner. Practitioners who work with low income, unmarried, nonresidential parents should conduct multi‐dimensional assessments that include both the negative and positive aspects of co‐parenting.