The aim of this short-term longitudinal study, based on the system theory, was to test the association between different aspects of family functioning of preschoolers and their socioaffective competencies at the end of the first grade. The total sample included 278 children (137 boys and 141 girls) and their families. The analysis of variance results regarding the aspects of family cohesion and harmony showed that preschoolers from more cohesive families display more social skills, while those from more conflicting families display more externalizing behavior problems (aggression and irritability). With respect to the family's ability to resolve problems, it was observed that, especially for middle and upper class families, this aspect is associated with better social skills and fewer internalized behavior problems. Overall, results of the present study suggest that the family functioning at early stage might influence children's abilities to regulate their emotions and to establish/maintain important relationships with peers and teachers in their early school years.