Witnessing intimate partner violence (IPV) among parents negatively impacts millions of children in the United States each year. Low-income families are disproportionately affected by IPV compared to middle- and high-income individuals, and are beginning to be the focus of IPV secondary prevention interventions, including relationship education programs. Despite these developments, few studies have examined changes in psychosocial functioning among children of parents participating in relationship education programs. The current study examined the extent to which changes in specific couple dynamics among individuals from low-income backgrounds participating in a couple relationship education program, Within My Reach, were associated with changes in child mental health symptoms. A second purpose of this paper is to examine whether changes in parent–child relationship quality mediates the association between changes in couple dynamics and changes in child mental health difficulties. Participants (n = 347) were parents who participated in Within My Reach as part of programming offered at a large community agency. Decreases in negative couple conflict behaviors, including conflict engagement, withdrawal and compliance, over the course of the program were linked to decreases in child mental health difficulties. In addition, increases in parent–child relationship quality partially mediated the associations between decreases in compliance, as well as increase in overall couple relationship quality, and decreases in child symptoms. Community-based couple relationship education programs for low-income families can potentially have multiple positive impacts throughout the family system, including for children.