<p>Adverse childhood experiences (ACEs) are a risk factor for negative parenting and children’s behavior problems. The present study examined the effects of the ACT-Raising Safe Kids Program on mothers’ parental practices and sense of competence, as well as children’s behaviors, comparing mothers with and without ACEs at different levels. The sample comprised 88 mothers with their 1–6-year-old children, divided into 3 groups: mothers with 4 or more ACEs (ACE^≥4 Group, <i>n</i> = 31), mothers with fewer than four ACEs (ACE^&lt;4 Group, <i>n</i> = 37), and mothers without ACEs (No-ACE Group, <i>n</i> = 20). The mothers participated in the intervention, which utilized the ACT Program (delivered in either in-person or online versions). Mothers completed the ACT, Parenting and Family Adjustment Scale, Parental Sense of Competence, and the Strengths and Difficulties Questionnaire at both the pre- and post-intervention stages. The three-way ANOVA for repeated measures was performed, controlled by socioeconomic status and maternal current depression symptoms. Regardless of the ACEs, the ACT Program showed positive effects on improving emotional and behavioral regulation, parent–child relationships, and parental sense of competence, as well as reducing coercive practices, in the post-intervention period compared to the pre-intervention period. Also, all mothers reported a reduction in children’s behavior problems, and, exclusively, mothers with ACEs mentioned an increase in prosocial behavior. Then, there were positive effects of the ACT Program on positive parenting and preventing violence against children, even among mothers with ACEs. The practical implication of the findings for prevention strategies is discussed.</p>