The present study evaluated the effectiveness of the Adults and Children Together (ACT) Raising Safe Kids Parenting Program for violence prevention in a developing country. The specific objectives were the following: (i) to compare parenting practices according to the mothers’ perceptions pre- and post-intervention and (ii) to compare child behavior problems and resources according to mothers’ and other caregivers’ perceptions pre- and post-intervention. The participants were 82 Brazilian mothers of 3- to 8-year-old children. Another caregiver of the child was included in the study as a second informer about child behavior (n = 72). Mothers participated in the ACT program and pre- and post-intervention evaluations. The other primary caregiver only participated in the two evaluations of child behavior. The results showed that parenting practices improved significantly from pre- to post-intervention. Mothers and the other primary caregivers reported a significant decrease in child behavior problems from pre- to post-intervention with regard to total behavioral difficulties, emotional symptoms, and peer relationship scales. Mothers also reported a significant decrease in scores for conduct problems and hyperactivity and improvements in child behavioral capabilities with regard to prosocial behavior. In conclusion, improvements on parenting practices and child behavior were observed after the ACT program.