The present study aimed to evaluate the effectiveness of a universal parenting program of violence prevention against children to improve the parenting practices in groups of mothers differentiated by the presence or not of a history of adverse childhood experiences. The study also aimed to characterize the types of violence experienced by the participants. A mixed-methods approach was used with qualitative and quantitative analyzes. The study sample consisted of 125 mothers of 3- to 8-year-old children. Mothers participated in the ACT-Raising Safe Kids Program with pre- and post-intervention evaluations. A self-report questionnaire was used to assess mothers’ parenting practices (emotional and behavioral regulation, communication, and positive discipline). After the intervention, an individual interview was carried out, including open-ended questions about the participants’ history of relationship with their parents and violence and maltreatment situations in their childhood. For the analysis, the mothers were divided into two groups, with a history of violence in childhood (VG; n = 103) and without violence in childhood (CG; n = 24). Results showed a high prevalence (81%) of mothers who reported violent episodes in their childhood, predominantly physical abuse. In the ACT post-intervention, both groups of mothers reported improvements in all dimensions of their parenting practices. In conclusion, the mothers improved their parenting practices after participation in a preventive program, regardless of their history of violence in childhood.