The article is focused on the study of the relationship between children’s theory of mind and the characteristics of their interaction with the caregiver in family. Based on the ideas about young children developing at an early age in the “mother–child” system, it was assumed that there is a correlation between the indicator of the theory of mind and the characteristics of interaction on the side of the mother, the child, and in the dyad. The study participants were 31 children without medical and biological risk factors aged 12 to 50 months (M(SD) = 28.6(8.98) months) and their mothers (30.7(6.38), 20 to 45 years old) with above-average education level, living mostly with an only child in a full family with average and above-average income. To assess the theory of mind, items extracted from the personal-social scale section of the BDI method (“Battelle Developmental Inventory”) were used, and a 5-minute videotape of their interaction was analyzed using the PCERA method (“The Parent-Child Early Relational Assessment”) to study the mother-child interaction. The results indicate a significant positive relationship of the theory of mind indicator in children with the characteristics of interaction on the part of mothers (expression of pleasure toward child during interaction, social initiatives, absence of negative physical contact), on the part of children (self-organization/self-regulation, adaptive abilities, persistence in achieving the goal, ability to focus and sustain attention, absence of focusing on the mother`s emotional state) and in dyad (absence of tension and anxiety). The findings are discussed in terms of the forming of children’s understanding of mental states in the context of their primary socio-emotional environment.