Caregivers' mentalization has gained importance in recent years, but most studies only include parental figures. Given empirical evidence showing the importance of educators in the development of preschoolers, this paper aims to assess how the mentalization and stress levels of parents and educational staff are related to attachment, ToM and social emotional development of children aged 3-4 years (M = 44.69 months, SD = 3.68, Gender = 53% girls) who attend preschool. A total of 146 preschoolers, their parents and 18 teachers are included in the sample. The results show higher levels of mentalization in educational staff compared to parents and positive relationship between the mentalization of both adults and ToM development in preschoolers. It was found a greater predictive weight of educational staff mentalization but this relation was mediated by family caregivers' mentalization and its contribution loses strength in those cases where the parent shows low mentalization level.