The primary source for young children's vocabulary development is parent-child interaction. How parent-child interaction influences vocabulary depends on the child's functioning and the family context. Although research shows the effect of the family context on vocabulary (e.g., reading activities at home, parental education), the role of a child's functioning has received less attention. Children's executive functioning (EF) influences how linguistic input is processed and their social functioning (SF) is important for maintaining social interaction. The aim of the present study was to investigate the additional contributions of children's EF and SF to vocabulary. EF, SF and family contextual factors were measured in 223 Dutch preschool children. EF and SF strongly predicted children's vocabulary in addition to their age, linguistic diversity at home and parental education. EF and SF are therefore important factors to take into account when investigating vocabulary and vocabulary interventions in preschool children.