Background <p>Children’s attachment is shaped by their mother’s mental health and their early life experiences. Motherhood evokes vulnerability, anxiety, anger, and helplessness. Poor maternal mental health may impede mothers from responding to their children’s needs.</p> Objective <p>The study aimed to examine the influence of maternal mental health and adverse childhood experiences (ACEs) on adult attachment anxiety and avoidance.</p> Participants and Setting <p>Adult participants (<i>n</i> = 317) were recruited through a small university in the southwest United States via social media, class announcements, and word of mouth on campus and in the surrounding community.</p> Methods <p>Participants completed online survey questions assessing their perceptions of their mothers’ mental health during childhood, ACEs, and adult attachment anxiety and avoidance. Hierarchical regressions were employed to evaluate the effects of ACEs and maternal mental health on predicting attachment anxiety and avoidance.</p> Results <p>The presence of ACEs showed a significant positive association with attachment anxiety and avoidance. Furthermore, the findings indicated poor maternal mental health during childhood was linked to higher levels of anxiety and avoidance in adulthood, over and above the presence of ACEs alone.</p> Conclusions <p>Maternal mental health combined with ACEs is a stronger predictor of insecure adult attachment than ACEs alone. These results underscore the importance of addressing maternal mental health in interventions aimed at promoting secure attachment in children. Early identification and support for mothers experiencing mental health challenges may mitigate the risk of insecure attachment in their children, thereby promoting healthy child development, with benefits that continue into adulthood.</p>