Early interventions and parenting programs have been found to be the most effective interventions in promoting wellbeing and preventing difficulties during childhood and adulthood, mainly because they operate in a sensitive period. Mentalization-based and video feedback interventions have shown their effectiveness in caregiver-child relationships. This study aimed to analyze the effect of a preventive mentalization-based intervention with video feedback on a group of Chilean mothers of preschool children compared with a control group. Fifthy mothers were assessed at baseline and at follow-up. Results showed that mothers of the experimental group reached lower levels of maternal stress and higher use of mental language, and that their children showed lower risk in their socio-emotional development.