ObjectivesMaternal mentalization refers to a mother's ability to consider her child as a subject with a mind and reflect this understanding through references to mental states in her speech with the child. Mentalization is relevant for a child's attachment and theory of mind. The aim of this research is to describe mentalization among a group of Chilean mothers with their children at two time periods -12 and 30 months of age-, analyze developmental changes between both ages and examine the relationship among maternal mentalization, the child's sex and temperament and the family socioeconomic status.MethodsThe research used a sample of 90 dyads, and the instruments utilized include a sociodemographic questionnaire, a mentalization assessment and Rothbart's temperament questionnaires (IBQ-R-VSF and ECBQ-VSF).ResultsThe results showed a decline in references to desires and physical states and an increase in causal talk and cognitions at 30 months of age compared to 12 months. In 12-month-old children, only the temperament dimension of negative affect demonstrated a relationship with factual talk and SES related to emotions. Whereas at 30 months, the dimensions of extraversion, regulation and child's sex related to references to desires, causal talk, emotions and physical states. The mothers' socioeconomic status (SES) related to references to desires.ConclusionsThe best predictor of change in mentalization between both ages was maternal education level.