|The purpose of this study is to evaluate the impact of the structure and quality of the co-residential co-parenting relationships on the self-efficacy of adolescent and young adult unmarried mothers. Forty one predominately low-income, African American mothers self-reported parental self-efficacy and relationship dynamics with their co-parenting partner, and participated in an hour-long focus group. Results found that mothers currently in an intragenerational co-parenting relationship or parenting alone scored higher on self-efficacy than those in an intergenerational relationship. In addition, mothers who reported more symmetry in their co-parenting relationship also reported higher self-efficacy scores. A qualitative analysis of focus group interviews reinforced quantitative findings and supported Bandura’s self-efficacy acquisition theory. Findings suggest that both the structure and quality of the mother’s relationship should be considered. Implications for mothers’ inferential definitions of co-parenting partners, and the way that researchers conceptualize co-parenting, especially in low resource populations are discussed.