There is now wide consensus that the quality of family relationships is involved in the development of child executive functioning (EF), a set of cognitive skills that bear critical importance for social and academic adjustment at school. This body of research has, however, focused almost exclusively on dyadic parent-child interactions and failed to consider higher-level family processes. Consequently, the current study focused on family alliance, that is, the degree of coordination that father, mother, and child achieve while interacting together, as a predictor of individual differences in children's EF. A community sample of 87 intact families (45 boys) participated in a triadic mother-father-child interaction when children were in kindergarten to assess family alliance. Children were assessed again when they were in Grade 4 with tasks of inhibition, cognitive flexibility, and working memory. Hierarchical regression analyses showed that higher-quality family alliance was predictive of better child performance on some cognitive flexibility and working memory tasks. These results indicate that some of the individual differences in child EF at school age may originate in the quality of the early family environment.