Prosocial behaviors refer to behaviors that are beneficial to others or have a positive impact on society, including sharing, helping, cooperating and comforting. Children will build a good peer relationship if they conduct prosocial behaviors frequently while reducing social withdrawal, aggression and other problematic behaviors. Because the prosocial behavior of children has its social adaptation value, it is of great theoretical and practical significance to understand the factors that affect the development of early prosocial behavior of children. According to the theory of socialized-family system, parent-child interaction experience may affect the development of children's theory of mind, which in turn influences their prosocial behaviors. With the changing social structure and the developing concept of gender equality, more fathers are now involved in the process of parenting and playing a unique role in the development of children's personality and socialization. As one of the main caregivers, paternal mind-mindedness may influence children's prosocial behaviors. Fathers with a higher ability of mind-mindedness may treat the child as an independent individual, respect the child’s psychological uniqueness when interacting with the child, and ly and sensitively capture and respond to the child’s internal needs, which helps positive parent-child relationship. The establishment of social security may also promote their children's understanding of themselves and others, make children more likely to empathize with others in interpersonal communication, and have more prosocial behaviors. Thus, this study aims to examine the relationship between paternal mind-mindedness and preschoolers’ prosocial behaviors, as well as the potential mediating role of preschooler’s theory of mind in this relationship. In this one-year longitudinal study, 130 preschoolers (Mage= 63.15 months, SD = 4.37) were randomly selected from two public preschools in Shanghai. At Time 1, the fathers completed the interview of mind-mindedness. At Time 2, the mothers completed the Strengths and Difficulties Questionnaire, and the children completed the false belief understanding task and Peabody Picture Vocabulary Test Revised (PPVT-R). Statistical analyses were performed using SPSS 23.0. Descriptive statistics were first obtained for variables of interest. Correlation analysis was subsequently used to examine the relationships among variables. SPSS PROCESS was used to examine the mediating role of children’s theory of mind. The major findings were as follows: (1) paternal mind-mindedness was significantly and positively correlated with preschooler’s prosocial behaviors and the theory of mind. (2) after controlling for preschooler’s gender, language ability, caregivers’ type, siblings, total number of paternal nonmental descriptions, preschoolers’ theory of mind had a significant mediating effect between paternal mind-mindedness and children's prosocial behavior. The direct effect of paternal mind-mindedness on children's prosocial behaviors was not significant. Thus, children’s mind-mindedness played a complete mediator role between paternal mind-mindedness and children’s prosocial behaviors. Present findings underscored the importance of paternal mind-mindedness in increasing preschoolers’ prosocial behaviors through heightening theory of mind. The study may have implications for practical work. For example, our findings suggest that parents, teachers, and professionals should pay attention to the improvement of children’s theory of mind in a targeted manner such as enhancing their fathers’ ability of mind-mindedness in the process of communication with their children.